From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <mattatobin@localhost.localdomain>
Date: Fri, 2 Feb 2018 04:16:08 -0500
Subject: Add m-esr52 at 52.6.0

---
 .../custom-elements/CustomElementRegistry.html     | 580 +++++++++++++++++++++
 .../custom-elements/HTMLElement-constructor.html   |  84 +++
 testing/web-platform/tests/custom-elements/OWNERS  |   9 +
 .../tests/custom-elements/adopted-callback.html    | 135 +++++
 .../attribute-changed-callback.html                | 223 ++++++++
 .../tests/custom-elements/connected-callbacks.html |  88 ++++
 .../custom-element-registry/define.html            | 243 +++++++++
 .../custom-elements/disconnected-callbacks.html    |  93 ++++
 .../custom-elements/htmlconstructor/newtarget.html | 124 +++++
 .../tests/custom-elements/reaction-timing.html     |  88 ++++
 .../tests/custom-elements/reactions/Attr.html      |  23 +
 .../tests/custom-elements/reactions/ChildNode.html |  35 ++
 .../custom-elements/reactions/DOMTokenList.html    | 217 ++++++++
 .../tests/custom-elements/reactions/Document.html  |  47 ++
 .../tests/custom-elements/reactions/Element.html   |  61 +++
 .../custom-elements/reactions/NamedNodeMap.html    |  39 ++
 .../tests/custom-elements/reactions/Node.html      |  49 ++
 .../custom-elements/reactions/ParentNode.html      |  27 +
 .../tests/custom-elements/reactions/Range.html     |  49 ++
 .../reactions/resources/reactions.js               | 217 ++++++++
 .../resources/custom-elements-helpers.js           | 162 ++++++
 .../resources/empty-html-document.html             |   5 +
 ...tom-elements-type-allowed-chars-first-char.html |  58 +++
 .../custom-elements-type-allowed-chars.html        |  54 ++
 .../v0/concepts/custom-elements-type-naming.html   |  65 +++
 .../new-registry-test.html                         |  39 ++
 .../no-registry-test.html                          |  48 ++
 .../share-registry-create-document.html            |  51 ++
 .../share-registry-import-document.html            |  95 ++++
 .../invoke-callbacks.html                          |  60 +++
 .../attached-callback-move-element-test.html       | 159 ++++++
 .../types-of-callbacks/attached-callback-test.html | 117 +++++
 ...ute-changed-callback-change-attribute-test.html | 229 ++++++++
 ...ute-changed-callback-remove-attribute-test.html | 166 ++++++
 ...ribute-changed-callback-set-attribute-test.html | 338 ++++++++++++
 .../created-callback-element-prototype-test.html   |  87 ++++
 .../created-callback-invocation-order-test.html    | 242 +++++++++
 .../created-callback-invocation-test.html          | 167 ++++++
 .../detached-callback-move-element-test.html       | 130 +++++
 ...detached-callback-no-browsing-context-test.html | 147 ++++++
 ...tached-callback-with-browsing-context-test.html |  85 +++
 .../v0/instantiating/changing-is-attribute.html    | 158 ++++++
 .../custom-element-constructor-is-attribute.html   |  49 ++
 .../custom-element-constructor-local-name.html     |  44 ++
 .../custom-element-constructor-namespace.html      |  43 ++
 .../custom-element-constructor-node-document.html  | 100 ++++
 .../custom-element-constructor-prototype.html      |  28 +
 .../v0/instantiating/custom-element-prototype.html |  30 ++
 .../custom-element-type-is-attribute.html          |  73 +++
 ...m-element-type-local-name-and-is-attribute.html | 101 ++++
 .../custom-element-type-local-name.html            |  38 ++
 ...ate-element-interface-type-is-a-local-name.html |  43 ++
 ...element-interface-type-is-a-type-extension.html |  69 +++
 .../create-element-is-attribute.html               |  71 +++
 .../create-element-namespace.html                  |  68 +++
 .../create-element-type-extension-is-a-type.html   |  47 ++
 .../create-element-type-extension-unresolved.html  |  49 ++
 .../create-element-type-is-a-local-name.html       |  38 ++
 .../created-callback-create-element-ns.html        |  72 +++
 .../created-callback-create-element.html           |  72 +++
 .../non-configurable-constructor-property.html     |  41 ++
 .../prototype-is-interface-prototype-object.html   |  44 ++
 .../v0/instantiating/unchanged-attribute.html      |  29 ++
 ...n-construction-algorithm-default-namespace.html |  43 ++
 ...onstruction-algorithm-duplicate-definition.html |  56 ++
 ...nition-construction-algorithm-invalid-type.html |  22 +
 ...nstruction-algorithm-local-name-lowercased.html |  32 ++
 ...nition-construction-algorithm-name-is-null.html |  40 ++
 ...nstruction-algorithm-no-interface-for-name.html |  26 +
 ...ction-algorithm-svg-namespace-name-is-null.html |  36 ++
 ...ition-construction-algorithm-svg-namespace.html |  26 +
 ...onstruction-algorithm-type-name-lowercased.html |  41 ++
 ...element-registration-algorithm-no-registry.html |  39 ++
 .../custom-element-name.html                       |  36 ++
 .../custom-element-prototype.html                  |  27 +
 ...lement-pseudoclass-css-test-custom-tag-ref.html |  16 +
 ...ed-element-pseudoclass-css-test-custom-tag.html |  23 +
 ...doclass-css-test-registered-custom-tag-ref.html |  16 +
 ...pseudoclass-css-test-registered-custom-tag.html |  26 +
 ...ass-css-test-registered-type-extension-ref.html |  16 +
 ...doclass-css-test-registered-type-extension.html |  33 ++
 ...nt-pseudoclass-css-test-type-extension-ref.html |  17 +
 ...lement-pseudoclass-css-test-type-extension.html |  23 +
 ...nt-pseudoclass-matching-query-selector-all.html | 190 +++++++
 ...lement-pseudoclass-matching-query-selector.html | 161 ++++++
 ...unresolved-elements-interface-html-element.html |  56 ++
 ...ed-elements-interface-html-unknown-element.html |  53 ++
 .../unresolved-elements-interface-svg-element.html |  47 ++
 .../tests/custom-elements/v0/resources/blank.html  |   9 +
 .../v0/resources/import-master-async.html          |  10 +
 .../v0/resources/import-master.html                |  10 +
 .../tests/custom-elements/v0/resources/import.html |   9 +
 .../register-and-create-custom-element.html        |  19 +
 .../custom-elements/v0/resources/x-element.html    |  10 +
 .../v0/resources/x-mathml-element.html             |  12 +
 .../v0/resources/x-svg-element.html                |  12 +
 .../tests/custom-elements/v0/testcommon.js         | 286 ++++++++++
 97 files changed, 7720 insertions(+)
 create mode 100644 testing/web-platform/tests/custom-elements/CustomElementRegistry.html
 create mode 100644 testing/web-platform/tests/custom-elements/HTMLElement-constructor.html
 create mode 100644 testing/web-platform/tests/custom-elements/OWNERS
 create mode 100644 testing/web-platform/tests/custom-elements/adopted-callback.html
 create mode 100644 testing/web-platform/tests/custom-elements/attribute-changed-callback.html
 create mode 100644 testing/web-platform/tests/custom-elements/connected-callbacks.html
 create mode 100644 testing/web-platform/tests/custom-elements/custom-element-registry/define.html
 create mode 100644 testing/web-platform/tests/custom-elements/disconnected-callbacks.html
 create mode 100644 testing/web-platform/tests/custom-elements/htmlconstructor/newtarget.html
 create mode 100644 testing/web-platform/tests/custom-elements/reaction-timing.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/Attr.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/ChildNode.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/DOMTokenList.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/Document.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/Element.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/NamedNodeMap.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/Node.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/ParentNode.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/Range.html
 create mode 100644 testing/web-platform/tests/custom-elements/reactions/resources/reactions.js
 create mode 100644 testing/web-platform/tests/custom-elements/resources/custom-elements-helpers.js
 create mode 100644 testing/web-platform/tests/custom-elements/resources/empty-html-document.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars-first-char.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-naming.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/new-registry-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/no-registry-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-create-document.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-import-document.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/enqueuing-and-invoking-callbacks/invoke-callbacks.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-move-element-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-change-attribute-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-remove-attribute-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-set-attribute-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-element-prototype-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-order-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-move-element-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-no-browsing-context-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-with-browsing-context-test.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/changing-is-attribute.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-is-attribute.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-local-name.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-namespace.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-node-document.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-prototype.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-prototype.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-is-attribute.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name-and-is-attribute.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-local-name.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-type-extension.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-is-attribute.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-namespace.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-is-a-type.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-unresolved.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-is-a-local-name.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element-ns.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/non-configurable-constructor-property.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/prototype-is-interface-prototype-object.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/instantiating/unchanged-attribute.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-default-namespace.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-duplicate-definition.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-invalid-type.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-local-name-lowercased.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-name-is-null.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-no-interface-for-name.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace-name-is-null.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-type-name-lowercased.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/element-registration-algorithm-no-registry.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-name.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-prototype.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag-ref.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag-ref.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension-ref.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension-ref.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector-all.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-unknown-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-svg-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/blank.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/import-master-async.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/import-master.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/import.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/register-and-create-custom-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/x-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/x-mathml-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/resources/x-svg-element.html
 create mode 100644 testing/web-platform/tests/custom-elements/v0/testcommon.js

(limited to 'testing/web-platform/tests/custom-elements')

diff --git a/testing/web-platform/tests/custom-elements/CustomElementRegistry.html b/testing/web-platform/tests/custom-elements/CustomElementRegistry.html
new file mode 100644
index 000000000..ecc7810e8
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/CustomElementRegistry.html
@@ -0,0 +1,580 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CustomElementRegistry interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="CustomElementRegistry interface must exist">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+test(function () {
+    assert_true('define' in CustomElementRegistry.prototype, '"define" exists on CustomElementRegistry.prototype');
+    assert_true('define' in customElements, '"define" exists on window.customElements');
+}, 'CustomElementRegistry interface must have define as a method');
+
+test(function () {
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', 1); },
+        'customElements.define must throw a TypeError when the element interface is a number');
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', '123'); },
+        'customElements.define must throw a TypeError when the element interface is a string');
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', {}); },
+        'customElements.define must throw a TypeError when the element interface is an object');
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('badname', []); },
+        'customElements.define must throw a TypeError when the element interface is an array');
+}, 'customElements.define must throw when the element interface is not a constructor');
+
+test(function () {
+    customElements.define('custom-html-element', HTMLElement);
+}, 'customElements.define must not throw the constructor is HTMLElement');
+
+test(function () {
+    class MyCustomElement extends HTMLElement {};
+
+    assert_throws({'name': 'SyntaxError'}, function () { customElements.define(null, MyCustomElement); },
+        'customElements.define must throw a SyntaxError if the tag name is null');
+    assert_throws({'name': 'SyntaxError'}, function () { customElements.define('', MyCustomElement); },
+        'customElements.define must throw a SyntaxError if the tag name is empty');
+    assert_throws({'name': 'SyntaxError'}, function () { customElements.define('abc', MyCustomElement); },
+        'customElements.define must throw a SyntaxError if the tag name does not contain "-"');
+    assert_throws({'name': 'SyntaxError'}, function () { customElements.define('a-Bc', MyCustomElement); },
+        'customElements.define must throw a SyntaxError if the tag name contains an upper case letter');
+
+    var builtinTagNames = [
+        'annotation-xml',
+        'color-profile',
+        'font-face',
+        'font-face-src',
+        'font-face-uri',
+        'font-face-format',
+        'font-face-name',
+        'missing-glyph'
+    ];
+
+    for (var tagName of builtinTagNames) {
+        assert_throws({'name': 'SyntaxError'}, function () { customElements.define(tagName, MyCustomElement); },
+            'customElements.define must throw a SyntaxError if the tag name is "' + tagName + '"');
+    }
+
+}, 'customElements.define must throw with an invalid name');
+
+test(function () {
+    class SomeCustomElement extends HTMLElement {};
+
+    var calls = [];
+    var OtherCustomElement = new Proxy(class extends HTMLElement {}, {
+        get: function (target, name) {
+            calls.push(name);
+            return target[name];
+        }
+    })
+
+    customElements.define('some-custom-element', SomeCustomElement);
+    assert_throws({'name': 'NotSupportedError'}, function () { customElements.define('some-custom-element', OtherCustomElement); },
+        'customElements.define must throw a NotSupportedError if the specified tag name is already used');
+    assert_array_equals(calls, [], 'customElements.define must validate the custom element name before getting the prototype of the constructor');
+
+}, 'customElements.define must throw when there is already a custom element of the same name');
+
+test(function () {
+    class AnotherCustomElement extends HTMLElement {};
+
+    customElements.define('another-custom-element', AnotherCustomElement);
+    assert_throws({'name': 'NotSupportedError'}, function () { customElements.define('some-other-element', AnotherCustomElement); },
+        'customElements.define must throw a NotSupportedError if the specified class already defines an element');
+
+}, 'customElements.define must throw a NotSupportedError when there is already a custom element with the same class');
+
+test(function () {
+    var outerCalls = [];
+    var OuterCustomElement = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            outerCalls.push(name);
+            customElements.define('inner-custom-element', InnerCustomElement);
+            return target[name];
+        }
+    });
+    var innerCalls = [];
+    var InnerCustomElement = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            outerCalls.push(name);
+            return target[name];
+        }
+    });
+
+    assert_throws({'name': 'NotSupportedError'}, function () { customElements.define('outer-custom-element', OuterCustomElement); },
+        'customElements.define must throw a NotSupportedError if the specified class already defines an element');
+    assert_array_equals(outerCalls, ['prototype'], 'customElements.define must get "prototype"');
+    assert_array_equals(innerCalls, [],
+        'customElements.define must throw a NotSupportedError when element definition is running flag is set'
+        + ' before getting the prototype of the constructor');
+
+}, 'customElements.define must throw a NotSupportedError when element definition is running flag is set');
+
+test(function () {
+    var calls = [];
+    var ElementWithBadInnerConstructor = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            calls.push(name);
+            customElements.define('inner-custom-element', 1);
+            return target[name];
+        }
+    });
+
+    assert_throws({'name': 'TypeError'}, function () {
+        customElements.define('element-with-bad-inner-constructor', ElementWithBadInnerConstructor);
+    }, 'customElements.define must throw a NotSupportedError if IsConstructor(constructor) is false');
+
+    assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
+}, 'customElements.define must check IsConstructor on the constructor before checking the element definition is running flag');
+
+test(function () {
+    var calls = [];
+    var ElementWithBadInnerName = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            calls.push(name);
+            customElements.define('badname', class extends HTMLElement {});
+            return target[name];
+        }
+    });
+
+    assert_throws({'name': 'SyntaxError'}, function () {
+        customElements.define('element-with-bad-inner-name', ElementWithBadInnerName);
+    }, 'customElements.define must throw a SyntaxError if the specified name is not a valid custom element name');
+
+    assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
+}, 'customElements.define must validate the custom element name before checking the element definition is running flag');
+
+test(function () {
+    var unresolvedElement = document.createElement('constructor-calls-define');
+    document.body.appendChild(unresolvedElement);
+    var elementUpgradedDuringUpgrade = document.createElement('defined-during-upgrade');
+    document.body.appendChild(elementUpgradedDuringUpgrade);
+
+    var DefinedDuringUpgrade = class extends HTMLElement { };
+
+    class ConstructorCallsDefine extends HTMLElement {
+        constructor() {
+            customElements.define('defined-during-upgrade', DefinedDuringUpgrade);
+            assert_false(unresolvedElement instanceof ConstructorCallsDefine);
+            assert_true(elementUpgradedDuringUpgrade instanceof DefinedDuringUpgrade);
+            super();
+            assert_true(unresolvedElement instanceof ConstructorCallsDefine);
+            assert_true(elementUpgradedDuringUpgrade instanceof DefinedDuringUpgrade);
+        }
+    }
+
+    assert_false(unresolvedElement instanceof ConstructorCallsDefine);
+    assert_false(elementUpgradedDuringUpgrade instanceof DefinedDuringUpgrade);
+
+    customElements.define('constructor-calls-define', ConstructorCallsDefine);
+}, 'customElements.define unset the element definition is running flag before upgrading custom elements');
+
+(function () {
+    var testCase = async_test('customElements.define must not throw'
+        +' when defining another custom element in a different global object during Get(constructor, "prototype")', {timeout: 100});
+
+    var iframe = document.createElement('iframe');
+    iframe.onload = function () {
+        testCase.step(function () {
+            var InnerCustomElement = class extends iframe.contentWindow.HTMLElement {};
+            var calls = [];
+            var proxy = new Proxy(class extends HTMLElement { }, {
+                get: function (target, name) {
+                    calls.push(name);
+                    iframe.contentWindow.customElements.define('another-custom-element', InnerCustomElement);
+                    return target[name];
+                }
+            })
+            customElements.define('element-with-inner-element-define', proxy);
+            assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
+            assert_true(iframe.contentDocument.createElement('another-custom-element') instanceof InnerCustomElement);
+        });
+        document.body.removeChild(iframe);
+        testCase.done();
+    }
+
+    document.body.appendChild(iframe);
+})();
+
+test(function () {
+    var calls = [];
+    var ElementWithBadInnerName = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            calls.push(name);
+            customElements.define('badname', class extends HTMLElement {});
+            return target[name];
+        }
+    });
+
+    assert_throws({'name': 'SyntaxError'}, function () {
+        customElements.define('element-with-bad-inner-name', ElementWithBadInnerName);
+    }, 'customElements.define must throw a SyntaxError if the specified name is not a valid custom element name');
+
+    assert_array_equals(calls, ['prototype'], 'customElements.define must get "prototype"');
+}, '');
+
+test(function () {
+    var calls = [];
+    var proxy = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            calls.push(name);
+            return target[name];
+        }
+    });
+    customElements.define('proxy-element', proxy);
+    assert_array_equals(calls, ['prototype']);
+}, 'customElements.define must get "prototype" property of the constructor');
+
+test(function () {
+    var proxy = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) {
+            throw {name: 'expectedError'};
+        }
+    });
+    assert_throws({'name': 'expectedError'}, function () { customElements.define('element-with-string-prototype', proxy); });
+}, 'customElements.define must rethrow an exception thrown while getting "prototype" property of the constructor');
+
+test(function () {
+    var returnedValue;
+    var proxy = new Proxy(class extends HTMLElement { }, {
+        get: function (target, name) { return returnedValue; }
+    });
+
+    returnedValue = null;
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
+        'customElements.define must throw when "prototype" property of the constructor is null');
+    returnedValue = undefined;
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
+        'customElements.define must throw when "prototype" property of the constructor is undefined');
+    returnedValue = 'hello';
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
+        'customElements.define must throw when "prototype" property of the constructor is a string');
+    returnedValue = 1;
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-string-prototype', proxy); },
+        'customElements.define must throw when "prototype" property of the constructor is a number');
+
+}, 'customElements.define must throw when "prototype" property of the constructor is not an object');
+
+test(function () {
+    var constructor = function () {}
+    var calls = [];
+    constructor.prototype = new Proxy(constructor.prototype, {
+        get: function (target, name) {
+            calls.push(name);
+            return target[name];
+        }
+    });
+    customElements.define('element-with-proxy-prototype', constructor);
+    assert_array_equals(calls, ['connectedCallback', 'disconnectedCallback', 'adoptedCallback', 'attributeChangedCallback']);
+}, 'customElements.define must get callbacks of the constructor prototype');
+
+test(function () {
+    var constructor = function () {}
+    var calls = [];
+    constructor.prototype = new Proxy(constructor.prototype, {
+        get: function (target, name) {
+            calls.push(name);
+            if (name == 'disconnectedCallback')
+                throw {name: 'expectedError'};
+            return target[name];
+        }
+    });
+    assert_throws({'name': 'expectedError'}, function () { customElements.define('element-with-throwing-callback', constructor); });
+    assert_array_equals(calls, ['connectedCallback', 'disconnectedCallback'],
+        'customElements.define must not get callbacks after one of the get throws');
+}, 'customElements.define must rethrow an exception thrown while getting callbacks on the constructor prototype');
+
+test(function () {
+    var constructor = function () {}
+    var calls = [];
+    constructor.prototype = new Proxy(constructor.prototype, {
+        get: function (target, name) {
+            calls.push(name);
+            if (name == 'adoptedCallback')
+                return 1;
+            return target[name];
+        }
+    });
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-throwing-callback', constructor); });
+    assert_array_equals(calls, ['connectedCallback', 'disconnectedCallback', 'adoptedCallback'],
+        'customElements.define must not get callbacks after one of the conversion throws');
+}, 'customElements.define must rethrow an exception thrown while converting a callback value to Function callback type');
+
+test(function () {
+    var constructor = function () {}
+    constructor.prototype.attributeChangedCallback = function () { };
+    var prototypeCalls = [];
+    var callOrder = 0;
+    constructor.prototype = new Proxy(constructor.prototype, {
+        get: function (target, name) {
+            if (name == 'prototype' || name == 'observedAttributes')
+                throw 'Unexpected access to observedAttributes';
+            prototypeCalls.push(callOrder++);    
+            prototypeCalls.push(name);
+            return target[name];
+        }
+    });
+    var constructorCalls = [];
+    var proxy = new Proxy(constructor, {
+        get: function (target, name) {
+            constructorCalls.push(callOrder++);    
+            constructorCalls.push(name);
+            return target[name];
+        }
+    });
+    customElements.define('element-with-attribute-changed-callback', proxy);
+    assert_array_equals(prototypeCalls, [1, 'connectedCallback', 2, 'disconnectedCallback', 3, 'adoptedCallback', 4, 'attributeChangedCallback']);
+    assert_array_equals(constructorCalls, [0, 'prototype', 5, 'observedAttributes']);
+}, 'customElements.define must get "observedAttributes" property on the constructor prototype when "attributeChangedCallback" is present');
+
+test(function () {
+    var constructor = function () {}
+    constructor.prototype.attributeChangedCallback = function () { };
+    var calls = [];
+    var proxy = new Proxy(constructor, {
+        get: function (target, name) {
+            calls.push(name);
+            if (name == 'observedAttributes')
+                throw {name: 'expectedError'};
+            return target[name];
+        }
+    });
+    assert_throws({'name': 'expectedError'}, function () { customElements.define('element-with-throwing-observed-attributes', proxy); });
+    assert_array_equals(calls, ['prototype', 'observedAttributes'],
+        'customElements.define must get "prototype" and "observedAttributes" on the constructor');
+}, 'customElements.define must rethrow an exception thrown while getting observedAttributes on the constructor prototype');
+
+test(function () {
+    var constructor = function () {}
+    constructor.prototype.attributeChangedCallback = function () { };
+    var calls = [];
+    var proxy = new Proxy(constructor, {
+        get: function (target, name) {
+            calls.push(name);
+            if (name == 'observedAttributes')
+                return 1;
+            return target[name];
+        }
+    });
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-invalid-observed-attributes', proxy); });
+    assert_array_equals(calls, ['prototype', 'observedAttributes'],
+        'customElements.define must get "prototype" and "observedAttributes" on the constructor');
+}, 'customElements.define must rethrow an exception thrown while converting the value of observedAttributes to sequence<DOMString>');
+
+test(function () {
+    var constructor = function () {}
+    constructor.prototype.attributeChangedCallback = function () { };
+    constructor.observedAttributes = {[Symbol.iterator]: function *() {
+        yield 'foo';
+        throw {name: 'SomeError'};
+    }};
+    assert_throws({'name': 'SomeError'}, function () { customElements.define('element-with-generator-observed-attributes', constructor); });
+}, 'customElements.define must rethrow an exception thrown while iterating over observedAttributes to sequence<DOMString>');
+
+test(function () {
+    var constructor = function () {}
+    constructor.prototype.attributeChangedCallback = function () { };
+    constructor.observedAttributes = {[Symbol.iterator]: 1};
+    assert_throws({'name': 'TypeError'}, function () { customElements.define('element-with-observed-attributes-with-uncallable-iterator', constructor); });
+}, 'customElements.define must rethrow an exception thrown while retrieving Symbol.iterator on observedAttributes');
+
+test(function () {
+    var constructor = function () {}
+    constructor.observedAttributes = 1;
+    customElements.define('element-without-callback-with-invalid-observed-attributes', constructor);
+}, 'customElements.define must not throw even if "observedAttributes" fails to convert if "attributeChangedCallback" is not defined');
+
+test(function () {
+    class MyCustomElement extends HTMLElement {};
+    customElements.define('my-custom-element', MyCustomElement);
+
+    var instance = new MyCustomElement;
+    assert_true(instance instanceof MyCustomElement,
+        'An instance of a custom HTML element be an instance of the associated interface');
+
+    assert_true(instance instanceof HTMLElement,
+        'An instance of a custom HTML element must inherit from HTMLElement');
+
+    assert_equals(instance.localName, 'my-custom-element',
+        'An instance of a custom element must use the associated tag name');
+
+    assert_equals(instance.namespaceURI, 'http://www.w3.org/1999/xhtml',
+        'A custom element HTML must use HTML namespace');
+
+}, 'customElements.define must define an instantiatable custom element');
+
+test(function () {
+    var disconnectedElement = document.createElement('some-custom');
+    var connectedElementBeforeShadowHost = document.createElement('some-custom');
+    var connectedElementAfterShadowHost = document.createElement('some-custom');
+    var elementInShadowTree = document.createElement('some-custom');
+    var childElementOfShadowHost = document.createElement('some-custom');
+    var customShadowHost = document.createElement('some-custom');
+    var elementInNestedShadowTree = document.createElement('some-custom');
+
+    var container = document.createElement('div');
+    var shadowHost = document.createElement('div');
+    var shadowRoot = shadowHost.attachShadow({mode: 'closed'});
+    container.appendChild(connectedElementBeforeShadowHost);
+    container.appendChild(shadowHost);
+    container.appendChild(connectedElementAfterShadowHost);
+    shadowHost.appendChild(childElementOfShadowHost);
+    shadowRoot.appendChild(elementInShadowTree);
+    shadowRoot.appendChild(customShadowHost);
+
+    var innerShadowRoot = customShadowHost.attachShadow({mode: 'closed'});
+    innerShadowRoot.appendChild(elementInNestedShadowTree);
+
+    var calls = [];
+    class SomeCustomElement extends HTMLElement {
+        constructor() {
+            super();
+            calls.push(this);
+        }
+    };
+
+    document.body.appendChild(container);
+    customElements.define('some-custom', SomeCustomElement);
+    assert_array_equals(calls, [connectedElementBeforeShadowHost, elementInShadowTree, customShadowHost, elementInNestedShadowTree, childElementOfShadowHost, connectedElementAfterShadowHost]);
+}, 'customElements.define must upgrade elements in the shadow-including tree order');
+
+test(function () {
+    assert_true('get' in CustomElementRegistry.prototype, '"get" exists on CustomElementRegistry.prototype');
+    assert_true('get' in customElements, '"get" exists on window.customElements');
+}, 'CustomElementRegistry interface must have get as a method');
+
+test(function () {
+    assert_equals(customElements.get('a-b'), undefined);
+}, 'customElements.get must return undefined when the registry does not contain an entry with the given name');
+
+test(function () {
+    assert_equals(customElements.get('html'), undefined);
+    assert_equals(customElements.get('span'), undefined);
+    assert_equals(customElements.get('div'), undefined);
+    assert_equals(customElements.get('g'), undefined);
+    assert_equals(customElements.get('ab'), undefined);
+}, 'customElements.get must return undefined when the registry does not contain an entry with the given name even if the name was not a valid custom element name');
+
+test(function () {
+    assert_equals(customElements.get('existing-custom-element'), undefined);
+    class ExistingCustomElement extends HTMLElement {};
+    customElements.define('existing-custom-element', ExistingCustomElement);
+    assert_equals(customElements.get('existing-custom-element'), ExistingCustomElement);
+}, 'customElements.get return the constructor of the entry with the given name when there is a matching entry.');
+
+test(function () {
+    assert_true(customElements.whenDefined('some-name') instanceof Promise);
+}, 'customElements.whenDefined must return a promise for a valid custom element name');
+
+test(function () {
+    assert_equals(customElements.whenDefined('some-name'), customElements.whenDefined('some-name'));
+}, 'customElements.whenDefined must return the same promise each time invoked for a valid custom element name which has not been defined');
+
+promise_test(function () {
+    var resolved = false;
+    var rejected = false;
+    customElements.whenDefined('a-b').then(function () { resolved = true; }, function () { rejected = true; });
+    return Promise.resolve().then(function () {
+        assert_false(resolved, 'The promise returned by "whenDefined" must not be resolved until a custom element is defined');
+        assert_false(rejected, 'The promise returned by "whenDefined" must not be rejected until a custom element is defined');
+    });    
+}, 'customElements.whenDefined must return an unresolved promise when the registry does not contain the entry with the given name')
+
+promise_test(function () {
+    var promise = customElements.whenDefined('badname');
+    promise.then(function (value) { promise.resolved = value; }, function (value) { promise.rejected = value; });
+
+    assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+    assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+
+    return Promise.resolve().then(function () {
+        assert_false('resolved' in promise, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
+        assert_true('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
+    });
+}, 'customElements.whenDefined must return a rejected promise when the given name is not a valid custom element name');
+
+promise_test(function () {
+    customElements.define('preexisting-custom-element', class extends HTMLElement { });
+
+    var promise = customElements.whenDefined('preexisting-custom-element');
+    promise.then(function (value) { promise.resolved = value; }, function (value) { promise.rejected = value; });
+
+    assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+    assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+
+    return Promise.resolve().then(function () {
+        assert_true('resolved' in promise, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
+        assert_equals(promise.resolved, undefined,
+            'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
+        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
+    });
+}, 'customElements.whenDefined must return a resolved promise when the registry contains the entry with the given name');
+
+promise_test(function () {
+    class AnotherExistingCustomElement extends HTMLElement {};
+    customElements.define('another-existing-custom-element', AnotherExistingCustomElement);
+
+    var promise1 = customElements.whenDefined('another-existing-custom-element');
+    var promise2 = customElements.whenDefined('another-existing-custom-element');
+    promise1.then(function (value) { promise1.resolved = value; }, function (value) { promise1.rejected = value; });
+    promise2.then(function (value) { promise2.resolved = value; }, function (value) { promise2.rejected = value; });
+
+    assert_not_equals(promise1, promise2);
+    assert_false('resolved' in promise1, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+    assert_false('resolved' in promise2, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+    assert_false('rejected' in promise1, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+    assert_false('rejected' in promise2, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+
+    return Promise.resolve().then(function () {
+        assert_true('resolved' in promise1, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
+        assert_equals(promise1.resolved, undefined, 'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
+        assert_false('rejected' in promise1, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
+
+        assert_true('resolved' in promise2, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
+        assert_equals(promise2.resolved, undefined, 'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
+        assert_false('rejected' in promise2, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
+    });
+}, 'customElements.whenDefined must return a new resolved promise each time invoked when the registry contains the entry with the given name');
+
+promise_test(function () {
+    var promise = customElements.whenDefined('element-defined-after-whendefined');
+    promise.then(function (value) { promise.resolved = value; }, function (value) { promise.rejected = value; });
+
+    assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+    assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+
+    var promiseAfterDefine;
+    return Promise.resolve().then(function () {
+        assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the element is defined');
+        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the element is defined');
+        assert_equals(customElements.whenDefined('element-defined-after-whendefined'), promise,
+            '"whenDefined" must return the same unresolved promise before the custom element is defined');
+        customElements.define('element-defined-after-whendefined', class extends HTMLElement { });
+        assert_false('resolved' in promise, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+
+        promiseAfterDefine = customElements.whenDefined('element-defined-after-whendefined');
+        promiseAfterDefine.then(function (value) { promiseAfterDefine.resolved = value; }, function (value) { promiseAfterDefine.rejected = value; });
+        assert_not_equals(promiseAfterDefine, promise, '"whenDefined" must return a resolved promise once the custom element is defined');
+        assert_false('resolved' in promiseAfterDefine, 'The promise returned by "whenDefined" must not be resolved until the end of the next microtask');
+        assert_false('rejected' in promiseAfterDefine, 'The promise returned by "whenDefined" must not be rejected until the end of the next microtask');
+    }).then(function () {
+        assert_true('resolved' in promise, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
+        assert_equals(promise.resolved, undefined,
+            'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
+        assert_false('rejected' in promise, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
+
+        assert_true('resolved' in promiseAfterDefine, 'The promise returned by "whenDefined" must be resolved when a custom element is defined');
+        assert_equals(promiseAfterDefine.resolved, undefined,
+            'The promise returned by "whenDefined" must be resolved with "undefined" when a custom element is defined');
+        assert_false('rejected' in promiseAfterDefine, 'The promise returned by "whenDefined" must not be rejected when a custom element is defined');
+    });
+}, 'A promise returned by customElements.whenDefined must be resolved by "define"');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/HTMLElement-constructor.html b/testing/web-platform/tests/custom-elements/HTMLElement-constructor.html
new file mode 100644
index 000000000..1ed625f63
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/HTMLElement-constructor.html
@@ -0,0 +1,84 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: HTMLElement must allow subclassing</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="HTMLElement must allow subclassing">
+<link rel="help" href="https://html.spec.whatwg.org/#html-element-constructors">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+test(function () {
+    customElements.define('html-custom-element', HTMLElement);
+    assert_throws({'name': 'TypeError'}, function () { new HTMLElement(); });
+}, 'HTMLElement constructor must throw a TypeError when NewTarget is equal to itself');
+
+test(function () {
+    customElements.define('html-proxy-custom-element', new Proxy(HTMLElement, {}));
+    assert_throws({'name': 'TypeError'}, function () { new HTMLElement(); });
+}, 'HTMLElement constructor must throw a TypeError when NewTarget is equal to itself via a Proxy object');
+
+test(function () {
+    class SomeCustomElement extends HTMLElement {};
+    assert_throws({'name': 'TypeError'}, function () { new SomeCustomElement; });
+}, 'HTMLElement constructor must throw TypeError when it has not been defined by customElements.define');
+
+test(function () {
+    class CustomElementWithInferredTagName extends HTMLElement {};
+    customElements.define('inferred-name', CustomElementWithInferredTagName);
+
+    var instance = new CustomElementWithInferredTagName;
+    assert_true(instance instanceof Element, 'A custom element must inherit from Element');
+    assert_true(instance instanceof Node, 'A custom element must inherit from Node');
+    assert_equals(instance.localName, 'inferred-name');
+    assert_equals(instance.nodeName, 'INFERRED-NAME');
+    assert_equals(instance.namespaceURI, 'http://www.w3.org/1999/xhtml', 'A custom HTML element must use HTML namespace');
+
+    document.body.appendChild(instance);
+    assert_equals(document.body.lastChild, instance,
+        'document.body.appendChild must be able to insert a custom element');
+    assert_equals(document.querySelector('inferred-name'), instance,
+        'document.querySelector must be able to find a custom element by its tag name');
+
+}, 'HTMLElement constructor must infer the tag name from the element interface');
+
+test(function () {
+    class ConcreteCustomElement extends HTMLElement { };
+    class SubCustomElement extends ConcreteCustomElement { };
+    customElements.define('concrete-custom-element', ConcreteCustomElement);
+    customElements.define('sub-custom-element', SubCustomElement);
+
+    var instance = new ConcreteCustomElement();
+    assert_true(instance instanceof ConcreteCustomElement);
+    assert_false(instance instanceof SubCustomElement);
+    assert_equals(instance.localName, 'concrete-custom-element');
+    assert_equals(instance.nodeName, 'CONCRETE-CUSTOM-ELEMENT');
+
+    var instance = new SubCustomElement();
+    assert_true(instance instanceof ConcreteCustomElement);
+    assert_true(instance instanceof SubCustomElement);
+    assert_equals(instance.localName, 'sub-custom-element');
+    assert_equals(instance.nodeName, 'SUB-CUSTOM-ELEMENT');
+
+}, 'HTMLElement constructor must allow subclassing a custom element');
+
+test(function () {
+    class AbstractCustomElement extends HTMLElement { };
+    class ConcreteSubCustomElement extends AbstractCustomElement { };
+    customElements.define('concrete-sub-custom-element', ConcreteSubCustomElement);
+
+    var instance = new ConcreteSubCustomElement();
+    assert_true(instance instanceof AbstractCustomElement);
+    assert_true(instance instanceof ConcreteSubCustomElement);
+    assert_equals(instance.localName, 'concrete-sub-custom-element');
+    assert_equals(instance.nodeName, 'CONCRETE-SUB-CUSTOM-ELEMENT');
+
+}, 'HTMLElement constructor must allow subclassing an user-defined subclass of HTMLElement');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/OWNERS b/testing/web-platform/tests/custom-elements/OWNERS
new file mode 100644
index 000000000..a8b25e79c
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/OWNERS
@@ -0,0 +1,9 @@
+@alsemenov
+@deepak-sa
+@domenic
+@dominiccooney
+@hayatoito
+@kojiishi
+@rniwa
+@sgrekhov
+@takayoshikochi
diff --git a/testing/web-platform/tests/custom-elements/adopted-callback.html b/testing/web-platform/tests/custom-elements/adopted-callback.html
new file mode 100644
index 000000000..5c08a04a4
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/adopted-callback.html
@@ -0,0 +1,135 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: adoptedCallback</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="adoptedCallback must be enqueued whenever custom element is adopted into a new document">
+<link rel="help" href="https://w3c.github.io/webcomponents/spec/custom/#dfn-connected-callback">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="./resources/custom-elements-helpers.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+var calls = [];
+class MyCustomElement extends HTMLElement {
+    connectedCallback() { calls.push('connected'); }
+    adoptedCallback(oldDocument, newDocument) { calls.push('adopted'); calls.push(oldDocument); calls.push(newDocument); }
+    disconnectedCallback() { calls.push('disconnected'); }
+}
+customElements.define('my-custom-element', MyCustomElement);
+
+test(function () {
+    var instance = document.createElement('my-custom-element');
+    calls = [];
+    document.body.appendChild(instance);
+    assert_array_equals(calls, ['connected']);
+}, 'Inserting a custom element into the owner document must not enqueue and invoke adoptedCallback');
+
+document_types().forEach(function (entry) {
+    if (entry.isOwner)
+        return;
+
+    var documentName = entry.name;
+    var getDocument = entry.create;
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            calls = [];
+            doc.documentElement.appendChild(instance);
+            assert_array_equals(calls, ['adopted', document, doc, 'connected']);
+        });
+    }, 'Inserting a custom element into ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            document.body.appendChild(instance);
+            calls = [];
+            doc.documentElement.appendChild(instance);
+            assert_array_equals(calls, ['disconnected', 'adopted', document, doc, 'connected']);
+        });
+    }, 'Moving a custom element from the owner document into ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var parent = document.createElement('div');
+            parent.appendChild(instance);
+            calls = [];
+            doc.documentElement.appendChild(parent);
+            assert_array_equals(calls, ['adopted', document, doc, 'connected']);
+        });
+    }, 'Inserting an ancestor of custom element into ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var parent = document.createElement('div');
+            parent.appendChild(instance);
+            document.body.appendChild(parent);
+            calls = [];
+            doc.documentElement.appendChild(parent);
+            assert_array_equals(calls, ['disconnected', 'adopted', document, doc, 'connected']);
+        });
+    }, 'Moving an ancestor of custom element from the owner document into ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            doc.documentElement.appendChild(host);
+
+            calls = [];
+            shadowRoot.appendChild(instance);
+            assert_array_equals(calls, ['adopted', document, doc, 'connected']);
+        });
+    }, 'Inserting a custom element into a shadow tree in ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = document.createElement('div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            shadowRoot.appendChild(instance);
+
+            calls = [];
+            doc.documentElement.appendChild(host);
+            assert_array_equals(calls, ['adopted', document, doc, 'connected']);
+        });
+    }, 'Inserting the shadow host of a custom element into ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = document.createElement('div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            shadowRoot.appendChild(instance);
+            document.body.appendChild(host);
+
+            calls = [];
+            doc.documentElement.appendChild(host);
+            assert_array_equals(calls, ['disconnected', 'adopted', document, doc, 'connected']);
+        });
+    }, 'Moving the shadow host of a custom element from the owner document into ' + documentName + ' must enqueue and invoke adoptedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+
+            calls = [];
+            shadowRoot.appendChild(instance);
+            assert_array_equals(calls, ['adopted', document, doc]);
+        });
+    }, 'Inserting a custom element into a detached shadow tree that belongs to ' + documentName + ' must enqueue and invoke adoptedCallback');
+});
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/attribute-changed-callback.html b/testing/web-platform/tests/custom-elements/attribute-changed-callback.html
new file mode 100644
index 000000000..bd467912b
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/attribute-changed-callback.html
@@ -0,0 +1,223 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: attributeChangedCallback</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="attributeChangedCallback must be enqueued whenever custom element's attribute is added, changed or removed">
+<link rel="help" href="https://w3c.github.io/webcomponents/spec/custom/#dfn-attribute-changed-callback">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="resources/custom-elements-helpers.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+var customElement = define_new_custom_element(['title', 'id', 'r']);
+
+test(function () {
+    const instance = document.createElement(customElement.name);
+    assert_array_equals(customElement.takeLog().types(), ['constructed']);
+
+    instance.setAttribute('title', 'foo');
+    assert_equals(instance.getAttribute('title'), 'foo');
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: null, newValue: 'foo', namespace: null});
+
+    instance.removeAttribute('title');
+    assert_equals(instance.getAttribute('title'), null);
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: 'foo', newValue: null, namespace: null});
+}, 'setAttribute and removeAttribute must enqueue and invoke attributeChangedCallback');
+
+test(function () {
+    var instance = document.createElement(customElement.name);
+    assert_array_equals(customElement.takeLog().types(), ['constructed']);
+
+    instance.setAttributeNS('http://www.w3.org/2000/svg', 'title', 'hello');
+    assert_equals(instance.getAttribute('title'), 'hello');
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: null, newValue: 'hello', namespace: 'http://www.w3.org/2000/svg'});
+
+    instance.removeAttributeNS('http://www.w3.org/2000/svg', 'title');
+    assert_equals(instance.getAttribute('title'), null);
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: 'hello', newValue: null, namespace: 'http://www.w3.org/2000/svg'});
+}, 'setAttributeNS and removeAttributeNS must enqueue and invoke attributeChangedCallback');
+
+test(function () {
+    var instance = document.createElement(customElement.name);
+    assert_array_equals(customElement.takeLog().types(), ['constructed']);
+
+    var attr = document.createAttribute('id');
+    attr.value = 'bar';
+    instance.setAttributeNode(attr);
+
+    assert_equals(instance.getAttribute('id'), 'bar');
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'id', oldValue: null, newValue: 'bar', namespace: null});
+
+    instance.removeAttributeNode(attr);
+    assert_equals(instance.getAttribute('id'), null);
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'id', oldValue: 'bar', newValue: null, namespace: null});
+}, 'setAttributeNode and removeAttributeNode must enqueue and invoke attributeChangedCallback for an HTML attribute');
+
+test(function () {
+    const instance = document.createElement(customElement.name);
+    assert_array_equals(customElement.takeLog().types(), ['constructed']);
+
+    const attr = document.createAttributeNS('http://www.w3.org/2000/svg', 'r');
+    attr.value = '100';
+    instance.setAttributeNode(attr);
+
+    assert_equals(instance.getAttribute('r'), '100');
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'r', oldValue: null, newValue: '100', namespace: 'http://www.w3.org/2000/svg'});
+
+    instance.removeAttributeNode(attr);
+    assert_equals(instance.getAttribute('r'), null);
+    var logEntries = customElement.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'r', oldValue: '100', newValue: null, namespace: 'http://www.w3.org/2000/svg'});
+}, 'setAttributeNode and removeAttributeNS must enqueue and invoke attributeChangedCallback for an SVG attribute');
+
+test(function () {
+    const callsToOld = [];
+    const callsToNew = [];
+    class CustomElement extends HTMLElement { }
+    CustomElement.prototype.attributeChangedCallback = function (...args) {
+        callsToOld.push(create_attribute_changed_callback_log(this, ...args));
+    }
+    CustomElement.observedAttributes = ['title'];
+    customElements.define('element-with-mutated-attribute-changed-callback', CustomElement);
+    CustomElement.prototype.attributeChangedCallback = function (...args) {
+        callsToNew.push(create_attribute_changed_callback_log(this, ...args));
+    }
+
+    const instance = document.createElement('element-with-mutated-attribute-changed-callback');
+    instance.setAttribute('title', 'hi');
+    assert_equals(instance.getAttribute('title'), 'hi');
+    assert_array_equals(callsToNew, []);
+    assert_equals(callsToOld.length, 1);
+    assert_attribute_log_entry(callsToOld[0], {name: 'title', oldValue: null, newValue: 'hi', namespace: null});
+}, 'Mutating attributeChangedCallback after calling customElements.define must not affect the callback being invoked');
+
+test(function () {
+    const calls = [];
+    class CustomElement extends HTMLElement {
+        attributeChangedCallback(...args) {
+            calls.push(create_attribute_changed_callback_log(this, ...args));
+        }
+    }
+    CustomElement.observedAttributes = ['title'];
+    customElements.define('element-not-observing-id-attribute', CustomElement);
+
+    const instance = document.createElement('element-not-observing-id-attribute');
+    assert_equals(calls.length, 0);
+    instance.setAttribute('title', 'hi');
+    assert_equals(calls.length, 1);
+    assert_attribute_log_entry(calls[0], {name: 'title', oldValue: null, newValue: 'hi', namespace: null});
+    instance.setAttribute('id', 'some');
+    assert_equals(calls.length, 1);
+    assert_attribute_log_entry(calls[0], {name: 'title', oldValue: null, newValue: 'hi', namespace: null});
+}, 'attributedChangedCallback must not be invoked when the observed attributes does not contain the attribute');
+
+test(function () {
+    const calls = [];
+    class CustomElement extends HTMLElement { }
+    CustomElement.prototype.attributeChangedCallback = function (...args) {
+        calls.push(create_attribute_changed_callback_log(this, ...args));
+    }
+    CustomElement.observedAttributes = ['title', 'lang'];
+    customElements.define('element-with-mutated-observed-attributes', CustomElement);
+    CustomElement.observedAttributes = ['title', 'id'];
+
+    const instance = document.createElement('element-with-mutated-observed-attributes');
+    instance.setAttribute('title', 'hi');
+    assert_equals(calls.length, 1);
+    assert_attribute_log_entry(calls[0], {name: 'title', oldValue: null, newValue: 'hi', namespace: null});
+
+    instance.setAttribute('id', 'some');
+    assert_equals(calls.length, 1);
+
+    instance.setAttribute('lang', 'en');
+    assert_equals(calls.length, 2);
+    assert_attribute_log_entry(calls[1], {name: 'lang', oldValue: null, newValue: 'en', namespace: null});
+}, 'Mutating observedAttributes after calling customElements.define must not affect the set of attributes for which attributedChangedCallback is invoked');
+
+test(function () {
+    var calls = [];
+    class CustomElement extends HTMLElement { }
+    CustomElement.prototype.attributeChangedCallback = function (...args) {
+        calls.push(create_attribute_changed_callback_log(this, ...args));
+    }
+    CustomElement.observedAttributes = { [Symbol.iterator]: function *() { yield 'lang'; yield 'style'; } };
+    customElements.define('element-with-generator-observed-attributes', CustomElement);
+
+    var instance = document.createElement('element-with-generator-observed-attributes');
+    instance.setAttribute('lang', 'en');
+    assert_equals(calls.length, 1);
+    assert_attribute_log_entry(calls[0], {name: 'lang', oldValue: null, newValue: 'en', namespace: null});
+
+    instance.setAttribute('lang', 'ja');
+    assert_equals(calls.length, 2);
+    assert_attribute_log_entry(calls[1], {name: 'lang', oldValue: 'en', newValue: 'ja', namespace: null});
+
+    instance.setAttribute('title', 'hello');
+    assert_equals(calls.length, 2);
+
+    instance.setAttribute('style', 'font-size: 2rem');
+    assert_equals(calls.length, 3);
+    assert_attribute_log_entry(calls[2], {name: 'style', oldValue: null, newValue: 'font-size: 2rem', namespace: null});
+}, 'attributedChangedCallback must be enqueued for attributes specified in a non-Array iterable observedAttributes');
+
+test(function () {
+    var calls = [];
+    class CustomElement extends HTMLElement { }
+    CustomElement.prototype.attributeChangedCallback = function (...args) {
+        calls.push(create_attribute_changed_callback_log(this, ...args));
+    }
+    CustomElement.observedAttributes = ['style'];
+    customElements.define('element-with-style-attribute-observation', CustomElement);
+
+    var instance = document.createElement('element-with-style-attribute-observation');
+    assert_equals(calls.length, 0);
+
+    instance.style.fontSize = '10px';
+    assert_equals(calls.length, 1);
+    assert_attribute_log_entry(calls[0], {name: 'style', oldValue: null, newValue: 'font-size: 10px;', namespace: null});
+
+    instance.style.fontSize = '20px';
+    assert_equals(calls.length, 2);
+    assert_attribute_log_entry(calls[1], {name: 'style', oldValue: 'font-size: 10px;', newValue: 'font-size: 20px;', namespace: null});
+
+}, 'attributedChangedCallback must be enqueued for style attribute change by mutating inline style declaration');
+
+test(function () {
+    var calls = [];
+    class CustomElement extends HTMLElement { }
+    CustomElement.prototype.attributeChangedCallback = function (...args) {
+        calls.push(create_attribute_changed_callback_log(this, ...args));
+    }
+    CustomElement.observedAttributes = ['title'];
+    customElements.define('element-with-no-style-attribute-observation', CustomElement);
+
+    var instance = document.createElement('element-with-no-style-attribute-observation');
+    assert_equals(calls.length, 0);
+    instance.style.fontSize = '10px';
+    assert_equals(calls.length, 0);
+    instance.title = 'hello';
+    assert_attribute_log_entry(calls[0], {name: 'title', oldValue: null, newValue: 'hello', namespace: null});
+}, 'attributedChangedCallback must not be enqueued when mutating inline style declaration if the style attribute is not observed');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/connected-callbacks.html b/testing/web-platform/tests/custom-elements/connected-callbacks.html
new file mode 100644
index 000000000..d6e68262a
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/connected-callbacks.html
@@ -0,0 +1,88 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: connectedCallback</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="connectedCallback must be enqueued whenever custom element is inserted into a document">
+<link rel="help" href="https://w3c.github.io/webcomponents/spec/custom/#dfn-connected-callback">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="resources/custom-elements-helpers.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+var calls = [];
+class MyCustomElement extends HTMLElement {
+    connectedCallback() { calls.push('connected', this); }
+    disconnectedCallback() { calls.push('disconnected', this); }
+}
+customElements.define('my-custom-element', MyCustomElement);
+
+document_types().forEach(function (entry) {
+    var documentName = entry.name;
+    var getDocument = entry.create;
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            calls = [];
+            doc.documentElement.appendChild(instance);
+            assert_array_equals(calls, ['connected', instance]);
+        });
+    }, 'Inserting a custom element into ' + documentName + ' must enqueue and invoke connectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var parent = document.createElement('div');
+            parent.appendChild(instance);
+            calls = [];
+            doc.documentElement.appendChild(parent);
+            assert_array_equals(calls, ['connected', instance]);
+        });
+    }, 'Inserting an ancestor of custom element into ' + documentName + ' must enqueue and invoke connectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            doc.documentElement.appendChild(host);
+
+            calls = [];
+            shadowRoot.appendChild(instance);
+            assert_array_equals(calls, ['connected', instance]);
+        });
+    }, 'Inserting a custom element into a shadow tree in ' + documentName + ' must enqueue and invoke connectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            shadowRoot.appendChild(instance);
+
+            calls = [];
+            doc.documentElement.appendChild(host);
+            assert_array_equals(calls, ['connected', instance]);
+        });
+    }, 'Inserting the shadow host of a custom element into ' + documentName + ' must enqueue and invoke connectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+
+            calls = [];
+            shadowRoot.appendChild(instance);
+            assert_array_equals(calls, []);
+        });
+    }, 'Inserting a custom element into a detached shadow tree that belongs to ' + documentName + ' must not enqueue and invoke connectedCallback');
+});
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/custom-element-registry/define.html b/testing/web-platform/tests/custom-elements/custom-element-registry/define.html
new file mode 100644
index 000000000..fedb68741
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/custom-element-registry/define.html
@@ -0,0 +1,243 @@
+<!DOCTYPE html>
+<title>Custom Elements: Element definition</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<body>
+<div id="log"></div>
+<iframe id="iframe"></iframe>
+<script>
+'use strict';
+(() =>  {
+  // Element definition
+  // https://html.spec.whatwg.org/multipage/scripting.html#element-definition
+
+  // Use window from iframe to isolate the test.
+  const testWindow = iframe.contentDocument.defaultView;
+  const customElements = testWindow.customElements;
+
+  let testable = false;
+  test(() =>  {
+    assert_true('customElements' in testWindow, '"window.customElements" exists');
+    assert_true('define' in customElements, '"window.customElements.define" exists');
+    testable = true;
+  }, '"window.customElements.define" should exists');
+  if (!testable)
+    return;
+
+  const expectTypeError = TypeError.prototype;
+  // Following errors are DOMException, not JavaScript errors.
+  const expectSyntaxError = 'SYNTAX_ERR';
+  const expectNotSupportedError = 'NOT_SUPPORTED_ERR';
+
+  // 1. If IsConstructor(constructor) is false,
+  // then throw a TypeError and abort these steps.
+  test(() =>  {
+    assert_throws(expectTypeError, () =>  {
+      customElements.define();
+    });
+  }, 'If no arguments, should throw a TypeError');
+  test(() =>  {
+    assert_throws(expectTypeError, () =>  {
+      customElements.define('test-define-one-arg');
+    });
+  }, 'If one argument, should throw a TypeError');
+  [
+    [ 'undefined', undefined ],
+    [ 'null', null ],
+    [ 'object', {} ],
+    [ 'string', 'string' ],
+    [ 'arrow function', () => {} ], // IsConstructor returns false for arrow functions
+    [ 'method', ({ m() { } }).m ], // IsConstructor returns false for methods
+  ].forEach(t =>  {
+    test(() =>  {
+      assert_throws(expectTypeError, () =>  {
+        customElements.define(`test-define-constructor-${t[0]}`, t[1]);
+      });
+    }, `If constructor is ${t[0]}, should throw a TypeError`);
+  });
+
+  // 2. If name is not a valid custom element name,
+  // then throw a SyntaxError and abort these steps.
+  let validCustomElementNames = [
+    // [a-z] (PCENChar)* '-' (PCENChar)*
+    // https://html.spec.whatwg.org/multipage/scripting.html#valid-custom-element-name
+    'a-',
+    'a-a',
+    'aa-',
+    'aa-a',
+    'a-.-_',
+    'a-0123456789',
+    'a-\u6F22\u5B57', // Two CJK Unified Ideographs
+    'a-\uD840\uDC0B', // Surrogate pair U+2000B
+  ];
+  let invalidCustomElementNames = [
+    undefined,
+    null,
+    '',
+    '-',
+    'a',
+    'input',
+    'mycustomelement',
+    'A',
+    'A-',
+    '0-',
+    'a-A',
+    'a-Z',
+    'A-a',
+    'a-a\u00D7',
+    'a-a\u3000',
+    'a-a\uDB80\uDC00', // Surrogate pair U+F0000
+    // name must not be any of the hyphen-containing element names.
+    'annotation-xml',
+    'color-profile',
+    'font-face',
+    'font-face-src',
+    'font-face-uri',
+    'font-face-format',
+    'font-face-name',
+    'missing-glyph',
+  ];
+  validCustomElementNames.forEach(name =>  {
+    test(() =>  {
+      customElements.define(name, class {});
+    }, `Element names: defining an element named ${name} should succeed`);
+  });
+  invalidCustomElementNames.forEach(name =>  {
+    test(() =>  {
+      assert_throws(expectSyntaxError, () =>  {
+        customElements.define(name, class {});
+      });
+    }, `Element names: defining an element named ${name} should throw a SyntaxError`);
+  });
+
+  // 3. If this CustomElementRegistry contains an entry with name name,
+  // then throw a NotSupportedError and abort these steps.
+  test(() =>  {
+    customElements.define('test-define-dup-name', class {});
+    assert_throws(expectNotSupportedError, () =>  {
+      customElements.define('test-define-dup-name', class {});
+    });
+  }, 'If the name is already defined, should throw a NotSupportedError');
+
+  // 5. If this CustomElementRegistry contains an entry with constructor constructor,
+  // then throw a NotSupportedError and abort these steps.
+  test(() =>  {
+    class TestDupConstructor {};
+    customElements.define('test-define-dup-constructor', TestDupConstructor);
+    assert_throws(expectNotSupportedError, () =>  {
+      customElements.define('test-define-dup-ctor2', TestDupConstructor);
+    });
+  }, 'If the constructor is already defined, should throw a NotSupportedError');
+
+  // 9.1. If extends is a valid custom element name,
+  // then throw a NotSupportedError.
+  validCustomElementNames.forEach(name =>  {
+    test(() =>  {
+      assert_throws(expectNotSupportedError, () =>  {
+        customElements.define('test-define-extend-valid-name', class {}, { extends: name });
+      });
+    }, `If extends is ${name}, should throw a NotSupportedError`);
+  });
+
+  // 9.2. If the element interface for extends and the HTML namespace is HTMLUnknownElement
+  // (e.g., if extends does not indicate an element definition in this specification),
+  // then throw a NotSupportedError.
+  [
+    // https://html.spec.whatwg.org/multipage/dom.html#elements-in-the-dom:htmlunknownelement
+    'bgsound',
+    'blink',
+    'isindex',
+    'multicol',
+    'nextid',
+    'spacer',
+    'elementnametobeunknownelement',
+  ].forEach(name =>  {
+    test(() =>  {
+      assert_throws(expectNotSupportedError, () =>  {
+        customElements.define('test-define-extend-' + name, class {}, { extends: name });
+      });
+    }, `If extends is ${name}, should throw a NotSupportedError`);
+  });
+
+  // 12.1. Let prototype be Get(constructor, "prototype"). Rethrow any exceptions.
+  function assert_rethrown(func, description) {
+    assert_throws({ name: 'rethrown' }, func, description);
+  }
+  function throw_rethrown_error() {
+    const e = new Error('check this is rethrown');
+    e.name = 'rethrown';
+    throw e;
+  }
+  test(() =>  {
+    // Hack for prototype to throw while IsConstructor is true.
+    const BadConstructor = (function () { }).bind({});
+    Object.defineProperty(BadConstructor, 'prototype', {
+      get() { throw_rethrown_error(); }
+    });
+    assert_rethrown(() =>  {
+      customElements.define('test-define-constructor-prototype-rethrow', BadConstructor);
+    });
+  }, 'If constructor.prototype throws, should rethrow');
+
+  // 12.2. If Type(prototype) is not Object,
+  // then throw a TypeError exception.
+  test(() =>  {
+    const c = (function () { }).bind({}); // prototype is undefined.
+    assert_throws(expectTypeError, () =>  {
+      customElements.define('test-define-constructor-prototype-undefined', c);
+    });
+  }, 'If Type(constructor.prototype) is undefined, should throw a TypeError');
+  test(() =>  {
+    function c() {};
+    c.prototype = 'string';
+    assert_throws(expectTypeError, () =>  {
+      customElements.define('test-define-constructor-prototype-string', c);
+    });
+  }, 'If Type(constructor.prototype) is string, should throw a TypeError');
+
+  // 12.3. Let lifecycleCallbacks be a map with the four keys "connectedCallback",
+  // "disconnectedCallback", "adoptedCallback", and "attributeChangedCallback",
+  // each of which belongs to an entry whose value is null.
+  // 12.4. For each of the four keys callbackName in lifecycleCallbacks:
+  // 12.4.1. Let callbackValue be Get(prototype, callbackName). Rethrow any exceptions.
+  // 12.4.2. If callbackValue is not undefined, then set the value of the entry in
+  // lifecycleCallbacks with key callbackName to the result of converting callbackValue
+  // to the Web IDL Function callback type. Rethrow any exceptions from the conversion.
+  [
+    'connectedCallback',
+    'disconnectedCallback',
+    'adoptedCallback',
+    'attributeChangedCallback',
+  ].forEach(name => {
+    test(() => {
+      class C {
+        get [name]() { throw_rethrown_error(); }
+      }
+      assert_rethrown(() => {
+        customElements.define(`test-define-${name.toLowerCase()}-rethrow`, C);
+      });
+    }, `If constructor.prototype.${name} throws, should rethrow`);
+
+    [
+      { name: 'undefined', value: undefined, success: true },
+      { name: 'function', value: function () { }, success: true },
+      { name: 'null', value: null, success: false },
+      { name: 'object', value: {}, success: false },
+      { name: 'integer', value: 1, success: false },
+    ].forEach(data => {
+      test(() => {
+        class C { };
+        C.prototype[name] = data.value;
+        if (data.success) {
+          customElements.define(`test-define-${name.toLowerCase()}-${data.name}`, C);
+        } else {
+          assert_throws(expectTypeError, () => {
+            customElements.define(`test-define-${name.toLowerCase()}-${data.name}`, C);
+          });
+        }
+      }, `If constructor.prototype.${name} is ${data.name}, should ${data.success ? 'succeed' : 'throw a TypeError'}`);
+    });
+  });
+})();
+</script>
+</body>
diff --git a/testing/web-platform/tests/custom-elements/disconnected-callbacks.html b/testing/web-platform/tests/custom-elements/disconnected-callbacks.html
new file mode 100644
index 000000000..7f5a4d0f8
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/disconnected-callbacks.html
@@ -0,0 +1,93 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: disconnectedCallback</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="disconnectedCallback must be enqueued whenever custom element is removed from a document">
+<link rel="help" href="https://w3c.github.io/webcomponents/spec/custom/#dfn-connected-callback">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="./resources/custom-elements-helpers.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+var calls = [];
+class MyCustomElement extends HTMLElement {
+    connectedCallback() { calls.push('connected', this); }
+    disconnectedCallback() { calls.push('disconnected', this); }
+}
+customElements.define('my-custom-element', MyCustomElement);
+
+document_types().forEach(function (entry) {
+    var documentName = entry.name;
+    var getDocument = entry.create;
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            doc.documentElement.appendChild(instance);
+            calls = [];
+            doc.documentElement.removeChild(instance);
+            assert_array_equals(calls, ['disconnected', instance]);
+        });
+    }, 'Removing a custom element from ' + documentName + ' must enqueue and invoke disconnectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var parent = document.createElement('div');
+            parent.appendChild(instance);
+            doc.documentElement.appendChild(parent);
+            calls = [];
+            doc.documentElement.removeChild(parent);
+            assert_array_equals(calls, ['disconnected', instance]);
+        });
+    }, 'Removing an ancestor of custom element from ' + documentName + ' must enqueue and invoke disconnectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            doc.documentElement.appendChild(host);
+            shadowRoot.appendChild(instance);
+
+            calls = [];
+            shadowRoot.removeChild(instance);
+            assert_array_equals(calls, ['disconnected', instance]);
+        });
+    }, 'Removing a custom element from a shadow tree in ' + documentName + ' must enqueue and invoke disconnectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            shadowRoot.appendChild(instance);
+            doc.documentElement.appendChild(host);
+
+            calls = [];
+            doc.documentElement.removeChild(host);
+            assert_array_equals(calls, ['disconnected', instance]);
+        });
+    }, 'Removing the shadow host of a custom element from a' + documentName + ' must enqueue and invoke disconnectedCallback');
+
+    promise_test(function () {
+        return getDocument().then(function (doc) {
+            var instance = document.createElement('my-custom-element');
+            var host = doc.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+            var shadowRoot = host.attachShadow({mode: 'closed'});
+            shadowRoot.appendChild(instance);
+
+            calls = [];
+            shadowRoot.removeChild(instance);
+            assert_array_equals(calls, []);
+        });
+    }, 'Removing a custom element from a detached shadow tree that belongs to ' + documentName + ' must not enqueue and invoke disconnectedCallback');
+});
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/htmlconstructor/newtarget.html b/testing/web-platform/tests/custom-elements/htmlconstructor/newtarget.html
new file mode 100644
index 000000000..04b4c4986
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/htmlconstructor/newtarget.html
@@ -0,0 +1,124 @@
+<!DOCTYPE html>
+<title>Custom Elements: [HTMLConstructor] derives prototype from NewTarget</title>
+<meta name="author" title="Domenic Denicola" href="mailto:d@domenic.me">
+<meta name="help" content="https://html.spec.whatwg.org/multipage/dom.html#htmlconstructor">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+
+<script>
+"use strict";
+
+test_with_window(w => {
+  let afterDefinition = false;
+  const proto1 = { "proto": "number one" };
+  const proto2 = { "proto": "number two" };
+
+  const TestElement = (function () {
+    assert_throws({ name: "prototype throws" }, () => {
+      const o = Reflect.construct(w.HTMLElement, [], new.target);
+
+      assert_equals(Object.getPrototypeOf(o), proto2,
+        "Must use the value returned from new.target.prototype");
+      assert_not_equals(Object.getPrototypeOf(o), proto1,
+        "Must not use the prototype stored at definition time");
+    });
+  }).bind({});
+
+  Object.defineProperty(TestElement, "prototype", {
+    get() {
+      return beforeDefinition ? proto1 : proto2;
+    }
+  });
+
+  w.customElements.define("test-element", TestElement);
+
+  beforeDefinition = true;
+  new TestElement();
+
+}, "Use NewTarget's prototype, not the one stored at definition time");
+
+test_with_window(w => {
+  // We have to not throw during define(), but throw during super()
+  let throws = false;
+
+  const TestElement = (function () {
+    assert_throws({ name: "prototype throws" }, () => {
+      return Reflect.construct(w.HTMLElement, [], new.target);
+    });
+  }).bind({});
+
+  Object.defineProperty(TestElement, "prototype", {
+    get() {
+      if (throws) {
+        throw { name: "prototype throws" };
+      }
+      return {};
+    }
+  });
+
+  w.customElements.define("test-element", TestElement);
+
+  throws = true;
+  new TestElement();
+
+}, "Rethrow any exceptions thrown while getting the prototype");
+
+test_with_window(w => {
+  for (const notAnObject of [null, undefined, 5, "string"]) {
+    // We have to return an object during define(), but not during super()
+    let returnNotAnObject = false;
+
+    const TestElement = (function () {
+      const o = Reflect.construct(w.HTMLElement, [], new.target);
+
+      assert_equals(Object.getPrototypeOf(o), window.HTMLElement,
+        "Must use the HTMLElement from the realm of NewTarget");
+      assert_not_equals(Object.getPrototypeOf(o), w.HTMLElement,
+        "Must not use the HTMLElement from the realm of the active function object (w.HTMLElement)");
+
+      return o;
+    }).bind({});
+
+    Object.defineProperty(TestElement, "prototype", {
+      get() {
+        return returnNotAnObject ? notAnObject : {};
+      }
+    });
+
+    w.customElements.define("test-element", TestElement);
+
+    returnNotAnObject = true;
+    new TestElement();
+  }
+}, "If prototype is not object, derives the fallback from NewTarget's realm (autonomous custom elements)");
+
+test_with_window(w => {
+  for (const notAnObject of [null, undefined, 5, "string"]) {
+    // We have to return an object during define(), but not during super()
+    let returnNotAnObject = false;
+
+    const TestElement = (function () {
+      const o = Reflect.construct(w.HTMLParagraphElement, [], new.target);
+
+      assert_equals(Object.getPrototypeOf(o), window.HTMLParagraphElement,
+        "Must use the HTMLParagraphElement from the realm of NewTarget");
+      assert_not_equals(Object.getPrototypeOf(o), w.HTMLParagraphElement,
+        "Must not use the HTMLParagraphElement from the realm of the active function object (w.HTMLParagraphElement)");
+
+      return o;
+    }).bind({});
+
+    Object.defineProperty(TestElement, "prototype", {
+      get() {
+        return returnNotAnObject ? notAnObject : {};
+      }
+    });
+
+    w.customElements.define("test-element", TestElement, { extends: "p" });
+
+    returnNotAnObject = true;
+    new TestElement();
+  }
+}, "If prototype is not object, derives the fallback from NewTarget's realm (customized built-in elements)");
+</script>
diff --git a/testing/web-platform/tests/custom-elements/reaction-timing.html b/testing/web-platform/tests/custom-elements/reaction-timing.html
new file mode 100644
index 000000000..9e5bafbed
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reaction-timing.html
@@ -0,0 +1,88 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: Custom element reactions must be invoked before returning to author scripts</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="Custom element reactions must be invoked before returning to author scripts">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/scripting.html#invoke-custom-element-reactions">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+class MyCustomElement extends HTMLElement {
+    attributeChangedCallback(...args) {
+        this.handler(...args);
+    }
+
+    handler() { }
+}
+MyCustomElement.observedAttributes = ['data-title', 'title'];
+customElements.define('my-custom-element', MyCustomElement);
+
+test(function () {
+    var instance = document.createElement('my-custom-element');
+    var anotherInstance = document.createElement('my-custom-element');
+
+    var callbackOrder = [];
+    instance.handler = function () {
+        callbackOrder.push([this, 'begin']);
+        anotherInstance.setAttribute('data-title', 'baz');
+        callbackOrder.push([this, 'end']);
+    }
+    anotherInstance.handler = function () {
+        callbackOrder.push([this, 'begin']);
+        callbackOrder.push([this, 'end']);
+    }
+
+    instance.setAttribute('title', 'foo');
+    assert_equals(callbackOrder.length, 4);
+
+    assert_array_equals(callbackOrder[0], [instance, 'begin']);
+    assert_array_equals(callbackOrder[1], [anotherInstance, 'begin']);
+    assert_array_equals(callbackOrder[2], [anotherInstance, 'end']);
+    assert_array_equals(callbackOrder[3], [instance, 'end']);
+
+}, 'setAttribute and removeAttribute must enqueue and invoke attributeChangedCallback');
+
+test(function () {
+    var shouldCloneAnotherInstance = false;
+    var anotherInstanceClone;
+    var log = [];
+
+    class SelfCloningElement extends HTMLElement {
+        constructor() {
+            super();
+            log.push([this, 'begin']);
+            if (shouldCloneAnotherInstance) {
+                shouldCloneAnotherInstance = false;
+                anotherInstanceClone = anotherInstance.cloneNode(false);
+            }
+            log.push([this, 'end']);
+        }
+    }
+    customElements.define('self-cloning-element', SelfCloningElement);
+
+    var instance = document.createElement('self-cloning-element');
+    var anotherInstance = document.createElement('self-cloning-element');
+    shouldCloneAnotherInstance = true;
+
+    assert_equals(log.length, 4);
+    var instanceClone = instance.cloneNode(false);
+
+    assert_equals(log.length, 8);
+    assert_array_equals(log[0], [instance, 'begin']);
+    assert_array_equals(log[1], [instance, 'end']);
+    assert_array_equals(log[2], [anotherInstance, 'begin']);
+    assert_array_equals(log[3], [anotherInstance, 'end']);
+    assert_array_equals(log[4], [instanceClone, 'begin']);
+    assert_array_equals(log[5], [anotherInstanceClone, 'begin']);
+    assert_array_equals(log[6], [anotherInstanceClone, 'end']);
+    assert_array_equals(log[7], [instanceClone, 'end']);
+}, 'Calling Node.prototype.cloneNode(false) must push a new element queue to the processing stack');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/Attr.html b/testing/web-platform/tests/custom-elements/reactions/Attr.html
new file mode 100644
index 000000000..c9fa37f96
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/Attr.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on Attr interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="value of Attr interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#node">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testAttributeMutator(function (element, name, value) {
+    element.attributes[name].value = value;
+}, 'value on Attr');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/ChildNode.html b/testing/web-platform/tests/custom-elements/reactions/ChildNode.html
new file mode 100644
index 000000000..756f17229
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/ChildNode.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on ChildNode interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="before, after, after, replaceWith, and remove of ChildNode interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#parentnode">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.firstChild.before(customElement);
+}, 'before on ChildNode');
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.firstChild.after(customElement);
+}, 'after on ChildNode');
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.firstChild.replaceWith(customElement);
+}, 'replaceWith on ChildNode');
+
+testNodeDisconnector(function (customElement) {
+    customElement.remove();
+}, 'replaceWith on ChildNode');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/DOMTokenList.html b/testing/web-platform/tests/custom-elements/reactions/DOMTokenList.html
new file mode 100644
index 000000000..38006d3e7
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/DOMTokenList.html
@@ -0,0 +1,217 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on DOMTokenList interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="add, remove, toggle, replace, and the stringifier of DOMTokenList interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#node">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<script>
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.add('foo');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: null, newValue: 'foo', namespace: null});
+}, 'add on DOMTokenList must enqueue an attributeChanged reaction when adding an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['style']);
+    var instance = document.createElement(element.name);
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.add('foo');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'add on DOMTokenList must not enqueue an attributeChanged reaction when adding an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.add('world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello', newValue: 'hello world', namespace: null});
+}, 'add on DOMTokenList must enqueue an attributeChanged reaction when adding a value to an existing attribute');
+
+test(function () {
+    var element = define_new_custom_element(['contenteditable']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.add('world');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'add on DOMTokenList must not enqueue an attributeChanged reaction when adding a value to an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.add('hello', 'world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: null, newValue: 'hello world', namespace: null});
+}, 'add on DOMTokenList must enqueue exactly one attributeChanged reaction when adding multiple values to an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello world');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.remove('world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello world', newValue: 'hello', namespace: null});
+}, 'remove on DOMTokenList must enqueue an attributeChanged reaction when removing a value from an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello foo world bar');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.remove('hello', 'world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello foo world bar', newValue: 'foo bar', namespace: null});
+}, 'remove on DOMTokenList must enqueue exactly one attributeChanged reaction when removing multiple values to an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello world');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.remove('foo');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'remove on DOMTokenList must not enqueue an attributeChanged reaction when removing a non-existent value from an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['title']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello world');
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.remove('world');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'remove on DOMTokenList must not enqueue an attributeChanged reaction when removing a value from an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.toggle('world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello', newValue: 'hello world', namespace: null});
+}, 'toggle on DOMTokenList must enqueue an attributeChanged reaction when adding a value to an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello world');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.toggle('world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello world', newValue: 'hello', namespace: null});
+}, 'toggle on DOMTokenList must enqueue an attributeChanged reaction when removing a value from an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['lang']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello world');
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.toggle('world');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'remove on DOMTokenList must not enqueue an attributeChanged reaction when removing a value from an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.replace('hello', 'world');
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello', newValue: 'world', namespace: null});
+}, 'replace on DOMTokenList must enqueue an attributeChanged reaction when replacing a value in an attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello world');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList.replace('foo', 'bar');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'replace on DOMTokenList must not enqueue an attributeChanged reaction when the token to replace does not exist in the attribute');
+
+test(function () {
+    var element = define_new_custom_element(['title']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList.replace('hello', 'world');
+    assert_array_equals(element.takeLog().types(), []);
+}, 'replace on DOMTokenList must not enqueue an attributeChanged reaction when replacing a value in an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList = 'hello';
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: null, newValue: 'hello', namespace: null});
+}, 'the stringifier of DOMTokenList must enqueue an attributeChanged reaction when adding an observed attribute');
+
+test(function () {
+    var element = define_new_custom_element(['id']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList = 'hello';
+    var logEntries = element.takeLog();
+    assert_array_equals(element.takeLog().types(), []);
+}, 'the stringifier of DOMTokenList must not enqueue an attributeChanged reaction when adding an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList = 'world';
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello', newValue: 'world', namespace: null});
+}, 'the stringifier of DOMTokenList must enqueue an attributeChanged reaction when mutating the value of an observed attribute');
+
+test(function () {
+    var element = define_new_custom_element([]);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+    instance.classList = 'world';
+    assert_array_equals(element.takeLog().types(), []);
+}, 'the stringifier of DOMTokenList must not enqueue an attributeChanged reaction when mutating the value of an unobserved attribute');
+
+test(function () {
+    var element = define_new_custom_element(['class']);
+    var instance = document.createElement(element.name);
+    instance.setAttribute('class', 'hello');
+    assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+    instance.classList = 'hello';
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['attributeChanged']);
+    assert_attribute_log_entry(logEntries.last(), {name: 'class', oldValue: 'hello', newValue: 'hello', namespace: null});
+}, 'the stringifier of DOMTokenList must enqueue an attributeChanged reaction when the setter is called with the original value of the attribute');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/Document.html b/testing/web-platform/tests/custom-elements/reactions/Document.html
new file mode 100644
index 000000000..304ec9861
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/Document.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on ParentNode interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="importNode and adoptNode of Document interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#document">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+test(function () {
+    var element = define_new_custom_element();
+    var instance = document.createElement(element.name);
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+
+    var newDoc = document.implementation.createHTMLDocument();
+    newDoc.importNode(instance);
+
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['constructed']);
+    assert_equals(logEntries.last().oldDocument, document);
+    assert_equals(logEntries.last().newDocument, newDoc);
+}, 'importNode on Document must construct a new custom element when importing a custom element');
+
+test(function () {
+    var element = define_new_custom_element();
+    var instance = document.createElement(element.name);
+    assert_array_equals(element.takeLog().types(), ['constructed']);
+
+    var newDoc = document.implementation.createHTMLDocument();
+    newDoc.adoptNode(instance);
+
+    var logEntries = element.takeLog();
+    assert_array_equals(logEntries.types(), ['adopted']);
+    assert_equals(logEntries.last().oldDocument, document);
+    assert_equals(logEntries.last().newDocument, newDoc);
+}, 'adoptNode on Document must enqueue an adopted reaction when importing a custom element');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/Element.html b/testing/web-platform/tests/custom-elements/reactions/Element.html
new file mode 100644
index 000000000..ed627f44e
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/Element.html
@@ -0,0 +1,61 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on Node interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="id, className, slot, setAttribute, setAttributeNS, removeAttribute, removeAttributeNS, setAttributeNode, setAttributeNodeNS, removeAttributeNode, and insertAdjacentElement of Element interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#element">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testReflectAttribute('id', 'id', 'foo', 'bar', 'id on Element');
+testReflectAttribute('className', 'class', 'foo', 'bar', 'className on Element');
+testReflectAttribute('slot', 'slot', 'foo', 'bar', 'slot on Element');
+
+testAttributeAdder(function (element, name, value) {
+    element.setAttribute(name, value);
+}, 'setAttribute on Element');
+
+testAttributeAdder(function (element, name, value) {
+    element.setAttributeNS(null, name, value);
+}, 'setAttributeNS on Element');
+
+testAttributeRemover(function (element, name) {
+    element.removeAttribute(name);
+}, 'removeAttribute on Element');
+
+testAttributeRemover(function (element, name) {
+    element.removeAttributeNS(null, name);
+}, 'removeAttributeNS on Element');
+
+testAttributeAdder(function (element, name, value) {
+    var attr = document.createAttribute(name);
+    attr.value = value;
+    element.setAttributeNode(attr);
+}, 'setAttributeNode on Element');
+
+testAttributeAdder(function (element, name, value) {
+    var attr = document.createAttribute(name);
+    attr.value = value;
+    element.setAttributeNodeNS(attr);
+}, 'setAttributeNodeNS on Element');
+
+testAttributeRemover(function (element, name) {
+    var attr = element.getAttributeNode(name);
+    if (attr)
+        element.removeAttributeNode(element.getAttributeNode(name));
+}, 'removeAttributeNode on Element');
+
+testNodeConnector(function (newContainer, element) {
+    newContainer.insertAdjacentElement('afterBegin', element);
+});
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/NamedNodeMap.html b/testing/web-platform/tests/custom-elements/reactions/NamedNodeMap.html
new file mode 100644
index 000000000..0ae83e9ab
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/NamedNodeMap.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on NamedNodeMap interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="setNamedItem, setNamedItemNS, removeNameditem, and removeNamedItemNS of NamedNodeMap interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#node">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testAttributeAdder(function (element, name, value) {
+    var attr = element.ownerDocument.createAttribute(name);
+    attr.value = value;
+    element.attributes.setNamedItem(attr);
+}, 'setNamedItem on NamedNodeMap');
+
+testAttributeAdder(function (element, name, value) {
+    var attr = element.ownerDocument.createAttribute(name);
+    attr.value = value;
+    element.attributes.setNamedItemNS(attr);
+}, 'setNamedItemNS on NamedNodeMap');
+
+testAttributeRemover(function (element, name) {
+    element.attributes.removeNamedItem(name);
+}, 'removeNamedItem on NamedNodeMap');
+
+testAttributeRemover(function (element, name) {
+    element.attributes.removeNamedItemNS(null, name);
+}, 'removeNamedItemNS on NamedNodeMap');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/Node.html b/testing/web-platform/tests/custom-elements/reactions/Node.html
new file mode 100644
index 000000000..94da3d020
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/Node.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on Node interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="nodeValue, textContent, normalize, cloneNode, insertBefore, appendChild, replaceChild, and removeChild of Node interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#node">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testAttributeMutator(function (element, name, value) {
+    element.getAttributeNode(name).nodeValue = value;
+}, 'nodeValue on Node');
+
+testAttributeMutator(function (element, name, value) {
+    element.getAttributeNode(name).textContent = value;
+}, 'textContent on Node');
+
+// FIXME: Add a test for normalize()
+
+testCloner(function (customElement) {
+    return customElement.cloneNode(false);
+}, 'cloneNode on Node');
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.insertBefore(customElement, newContainer.firstChild);
+}, 'insertBefore on ChildNode');
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.appendChild(customElement);
+}, 'appendChild on ChildNode');
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.replaceChild(customElement, newContainer.firstChild);
+}, 'replaceChild on ChildNode');
+
+testNodeDisconnector(function (customElement) {
+    customElement.parentNode.removeChild(customElement);
+}, 'removeChild on ChildNode');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/ParentNode.html b/testing/web-platform/tests/custom-elements/reactions/ParentNode.html
new file mode 100644
index 000000000..b143b5a98
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/ParentNode.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on ParentNode interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="prepend and append of ParentNode interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#parentnode">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.prepend(customElement);
+}, 'prepend on ParentNode');
+
+testNodeConnector(function (newContainer, customElement) {
+    newContainer.append(customElement);
+}, 'append on ParentNode');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/Range.html b/testing/web-platform/tests/custom-elements/reactions/Range.html
new file mode 100644
index 000000000..82382d520
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/Range.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom Elements: CEReactions on Range interface</title>
+<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
+<meta name="assert" content="deleteContents, extractContents, cloneContents, insertNode, and surroundContents of Range interface must have CEReactions">
+<meta name="help" content="https://dom.spec.whatwg.org/#node">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<script src="./resources/reactions.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+
+testNodeDisconnector(function (customElement) {
+    var range = document.createRange();
+    range.selectNode(customElement);
+    range.deleteContents();
+}, 'deleteContents on Range');
+
+testNodeDisconnector(function (customElement) {
+    var range = document.createRange();
+    range.selectNode(customElement);
+    range.extractContents();
+}, 'extractContents on Range');
+
+testCloner(function (customElement) {
+    var range = document.createRange();
+    range.selectNode(customElement);
+    range.cloneContents();
+}, 'cloneContents on Range')
+
+testNodeConnector(function (container, customElement) {
+    var range = document.createRange();
+    range.selectNodeContents(container);
+    range.insertNode(customElement);
+}, 'insertNode on Range');
+
+testNodeConnector(function (container, customElement) {
+    var range = document.createRange();
+    range.selectNodeContents(container);
+    range.surroundContents(customElement);
+}, 'insertNode on Range');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/reactions/resources/reactions.js b/testing/web-platform/tests/custom-elements/reactions/resources/reactions.js
new file mode 100644
index 000000000..c260dc4f3
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/reactions/resources/reactions.js
@@ -0,0 +1,217 @@
+
+let testNumber = 1;
+
+function testNodeConnector(testFunction, name) {
+    let container = document.createElement('div');
+    container.appendChild(document.createElement('div'));
+    document.body.appendChild(container);
+
+    test(function () {
+        var element = define_new_custom_element();
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(container, instance);
+        assert_array_equals(element.takeLog().types(), ['connected']);
+    }, name + ' must enqueue a connected reaction');
+
+    test(function () {
+        var element = define_new_custom_element();
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        var newDoc = document.implementation.createHTMLDocument();
+        testFunction(container, instance);
+        assert_array_equals(element.takeLog().types(), ['connected']);
+        testFunction(newDoc.documentElement, instance);
+        assert_array_equals(element.takeLog().types(), ['disconnected', 'adopted', 'connected']);
+    }, name + ' must enqueue a disconnected reaction, an adopted reaction, and a connected reaction when the custom element was in another document');
+
+    container.parentNode.removeChild(container);
+}
+
+function testNodeDisconnector(testFunction, name) {
+    let container = document.createElement('div');
+    container.appendChild(document.createElement('div'));
+    document.body.appendChild(container);
+ 
+    test(function () {
+        var element = define_new_custom_element();
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        container.appendChild(instance);
+        assert_array_equals(element.takeLog().types(), ['connected']);
+        testFunction(instance);
+        assert_array_equals(element.takeLog().types(), ['disconnected']);
+    }, name + ' must enqueue a disconnected reaction');
+
+    container.parentNode.removeChild(container);
+}
+
+function testCloner(testFunction, name) {
+    let container = document.createElement('div');
+    container.appendChild(document.createElement('div'));
+    document.body.appendChild(container);
+
+    test(function () {
+        var element = define_new_custom_element(['id']);
+        var instance = document.createElement(element.name);
+        container.appendChild(instance);
+
+        instance.setAttribute('id', 'foo');
+        assert_array_equals(element.takeLog().types(), ['constructed', 'connected', 'attributeChanged']);
+        var newInstance = testFunction(instance);
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['constructed', 'attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: 'id', oldValue: null, newValue: 'foo', namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when cloning an element with an observed attribute');
+
+    test(function () {
+        var element = define_new_custom_element(['id']);
+        var instance = document.createElement(element.name);
+        container.appendChild(instance);
+
+        instance.setAttribute('lang', 'en');
+        assert_array_equals(element.takeLog().types(), ['constructed', 'connected']);
+        var newInstance = testFunction(instance);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+    }, name + ' must not enqueue an attributeChanged reaction when cloning an element with an unobserved attribute');
+
+    test(function () {
+        var element = define_new_custom_element(['title', 'class']);
+        var instance = document.createElement(element.name);
+        container.appendChild(instance);
+
+        instance.setAttribute('lang', 'en');
+        instance.className = 'foo';
+        instance.setAttribute('title', 'hello world');
+        assert_array_equals(element.takeLog().types(), ['constructed', 'connected', 'attributeChanged', 'attributeChanged']);
+        var newInstance = testFunction(instance);
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['constructed', 'attributeChanged', 'attributeChanged']);
+        assert_attribute_log_entry(logEntries[1], {name: 'class', oldValue: null, newValue: 'foo', namespace: null});
+        assert_attribute_log_entry(logEntries[2], {name: 'title', oldValue: null, newValue: 'hello world', namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when cloning an element only for observed attributes');
+}
+
+function testReflectAttribute(jsAttributeName, contentAttributeName, validValue1, validValue2, name) {
+    test(function () {
+        var element = define_new_custom_element([contentAttributeName]);
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        instance[jsAttributeName] = validValue1;
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: contentAttributeName, oldValue: null, newValue: validValue1, namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when adding ' + contentAttributeName + ' content attribute');
+
+    test(function () {
+        var element = define_new_custom_element([contentAttributeName]);
+        var instance = document.createElement(element.name);
+        instance[jsAttributeName] = validValue1;
+        assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+        instance[jsAttributeName] = validValue2;
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: contentAttributeName, oldValue: validValue1, newValue: validValue2, namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when replacing an existing attribute');
+}
+
+function testAttributeAdder(testFunction, name) {
+    test(function () {
+        var element = define_new_custom_element(['id']);
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'id', 'foo');
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: 'id', oldValue: null, newValue: 'foo', namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when adding an attribute');
+
+    test(function () {
+        var element = define_new_custom_element(['class']);
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'data-lang', 'en');
+        assert_array_equals(element.takeLog().types(), []);
+    }, name + ' must not enqueue an attributeChanged reaction when adding an unobserved attribute');
+
+    test(function () {
+        var element = define_new_custom_element(['title']);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('title', 'hello');
+        assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+        testFunction(instance, 'title', 'world');
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: 'hello', newValue: 'world', namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when replacing an existing attribute');
+
+    test(function () {
+        var element = define_new_custom_element([]);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('data-lang', 'zh');
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'data-lang', 'en');
+        assert_array_equals(element.takeLog().types(), []);
+    }, name + ' must enqueue an attributeChanged reaction when replacing an existing unobserved attribute');
+}
+
+function testAttributeMutator(testFunction, name) {
+    test(function () {
+        var element = define_new_custom_element(['title']);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('title', 'hello');
+        assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+        testFunction(instance, 'title', 'world');
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: 'hello', newValue: 'world', namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when replacing an existing attribute');
+
+    test(function () {
+        var element = define_new_custom_element(['class']);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('data-lang', 'zh');
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'data-lang', 'en');
+        assert_array_equals(element.takeLog().types(), []);
+    }, name + ' must not enqueue an attributeChanged reaction when replacing an existing unobserved attribute');
+}
+
+function testAttributeRemover(testFunction, name) {
+    test(function () {
+        var element = define_new_custom_element(['title']);
+        var instance = document.createElement(element.name);
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'title');
+        assert_array_equals(element.takeLog().types(), []);
+    }, name + ' must not enqueue an attributeChanged reaction when removing an attribute that does not exist');
+
+    test(function () {
+        var element = define_new_custom_element([]);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('data-lang', 'hello');
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'data-lang');
+        assert_array_equals(element.takeLog().types(), []);
+    }, name + ' must not enqueue an attributeChanged reaction when removing an unobserved attribute');
+
+    test(function () {
+        var element = define_new_custom_element(['title']);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('title', 'hello');
+        assert_array_equals(element.takeLog().types(), ['constructed', 'attributeChanged']);
+        testFunction(instance, 'title');
+        var logEntries = element.takeLog();
+        assert_array_equals(logEntries.types(), ['attributeChanged']);
+        assert_attribute_log_entry(logEntries.last(), {name: 'title', oldValue: 'hello', newValue: null, namespace: null});
+    }, name + ' must enqueue an attributeChanged reaction when removing an existing attribute');
+
+    test(function () {
+        var element = define_new_custom_element([]);
+        var instance = document.createElement(element.name);
+        instance.setAttribute('data-lang', 'ja');
+        assert_array_equals(element.takeLog().types(), ['constructed']);
+        testFunction(instance, 'data-lang');
+        assert_array_equals(element.takeLog().types(), []);
+    }, name + ' must not enqueue an attributeChanged reaction when removing an existing unobserved attribute');
+}
diff --git a/testing/web-platform/tests/custom-elements/resources/custom-elements-helpers.js b/testing/web-platform/tests/custom-elements/resources/custom-elements-helpers.js
new file mode 100644
index 000000000..63fb98b43
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/resources/custom-elements-helpers.js
@@ -0,0 +1,162 @@
+function create_window_in_test(t, srcdoc) {
+  let p = new Promise((resolve) => {
+    let f = document.createElement('iframe');
+    f.srcdoc = srcdoc ? srcdoc : '';
+    f.onload = (event) => {
+      let w = f.contentWindow;
+      t.add_cleanup(() => f.parentNode && f.remove());
+      resolve(w);
+    };
+    document.body.appendChild(f);
+  });
+  return p;
+}
+
+function test_with_window(f, name, srcdoc) {
+  promise_test((t) => {
+    return create_window_in_test(t, srcdoc)
+    .then((w) => {
+      f(w);
+    });
+  }, name);
+}
+
+function create_attribute_changed_callback_log(element, name, oldValue, newValue, namespace) {
+    return {
+        type: 'attributeChanged',
+        element: element,
+        name: name,
+        namespace: namespace,
+        oldValue: oldValue,
+        newValue: newValue,
+        actualValue: element.getAttributeNS(namespace, name)
+    };
+}
+
+function assert_attribute_log_entry(log, expected) {
+    assert_equals(log.type, 'attributeChanged');
+    assert_equals(log.name, expected.name);
+    assert_equals(log.oldValue, expected.oldValue);
+    assert_equals(log.newValue, expected.newValue);
+    assert_equals(log.actualValue, expected.newValue);
+    assert_equals(log.namespace, expected.namespace);
+}
+
+
+function define_new_custom_element(observedAttributes) {
+    let log = [];
+    let name = 'custom-element-' + define_new_custom_element._element_number++;
+
+    class CustomElement extends HTMLElement {
+        constructor() {
+            super();
+            log.push({type: 'constructed', element: this});
+        }
+        attributeChangedCallback(...args) {
+            log.push(create_attribute_changed_callback_log(this, ...args));
+        }
+        connectedCallback() { log.push({type: 'connected', element: this}); }
+        disconnectedCallback() { log.push({type: 'disconnected', element: this}); }
+        adoptedCallback(oldDocument, newDocument) { log.push({type: 'adopted', element: this, oldDocument: oldDocument, newDocument: newDocument}); }
+    }
+    CustomElement.observedAttributes = observedAttributes;
+
+    customElements.define(name, CustomElement);
+
+    return {
+        name: name,
+        takeLog: function () {
+            let currentLog = log; log = [];
+            currentLog.types = () => currentLog.map((entry) => entry.type);
+            currentLog.last = () => currentLog[currentLog.length - 1];
+            return currentLog;
+        }
+    };
+}
+define_new_custom_element._element_number = 1;
+
+function document_types() {
+    return [
+        {
+            name: 'the document',
+            create: function () { return Promise.resolve(document); },
+            isOwner: true,
+            hasBrowsingContext: true,
+        },
+        {
+            name: 'the document of the template elements',
+            create: function () {
+                return new Promise(function (resolve) {
+                    var template = document.createElementNS('http://www.w3.org/1999/xhtml', 'template');
+                    var doc = template.content.ownerDocument;
+                    if (!doc.documentElement)
+                        doc.appendChild(doc.createElement('html'));
+                    resolve(doc);
+                });
+            },
+            hasBrowsingContext: false,
+        },
+        {
+            name: 'a new document',
+            create: function () {
+                return new Promise(function (resolve) {
+                    var doc = new Document();
+                    doc.appendChild(doc.createElement('html'));
+                    resolve(doc);
+                });
+            },
+            hasBrowsingContext: false,
+        },
+        {
+            name: 'a cloned document',
+            create: function () {
+                return new Promise(function (resolve) {
+                    var doc = document.cloneNode(false);
+                    doc.appendChild(doc.createElement('html'));
+                    resolve(doc);
+                });
+            },
+            hasBrowsingContext: false,
+        },
+        {
+            name: 'a document created by createHTMLDocument',
+            create: function () {
+                return Promise.resolve(document.implementation.createHTMLDocument());
+            },
+            hasBrowsingContext: false,
+        },
+        {
+            name: 'an HTML document created by createDocument',
+            create: function () {
+                return Promise.resolve(document.implementation.createDocument('http://www.w3.org/1999/xhtml', 'html', null));
+            },
+            hasBrowsingContext: false,
+        },
+        {
+            name: 'the document of an iframe',
+            create: function () {
+                return new Promise(function (resolve, reject) {
+                    var iframe = document.createElement('iframe');
+                    iframe.onload = function () { resolve(iframe.contentDocument); }
+                    iframe.onerror = function () { reject('Failed to load an empty iframe'); }
+                    document.body.appendChild(iframe);
+                });
+            },
+            hasBrowsingContext: true,
+        },
+        {
+            name: 'an HTML document fetched by XHR',
+            create: function () {
+                return new Promise(function (resolve, reject) {
+                    var xhr = new XMLHttpRequest();
+                    xhr.open('GET', 'resources/empty-html-document.html');
+                    xhr.overrideMimeType('text/xml');
+                    xhr.onload = function () { resolve(xhr.responseXML); }
+                    xhr.onerror = function () { reject('Failed to fetch the document'); }
+                    xhr.send();
+                });
+            },
+            hasBrowsingContext: false,
+        }
+    ];
+}
diff --git a/testing/web-platform/tests/custom-elements/resources/empty-html-document.html b/testing/web-platform/tests/custom-elements/resources/empty-html-document.html
new file mode 100644
index 000000000..eaca3f49f
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/resources/empty-html-document.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<html>
+<body>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars-first-char.html b/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars-first-char.html
new file mode 100644
index 000000000..b83b5fa78
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars-first-char.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>First char allowed for custom element type </title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="The custom element type identifies a custom element interface and is a sequence of characters that must match the NCName production">
+<meta name="timeout" content="long">
+<link rel="help" href="https://dvcs.w3.org/hg/webcomponents/raw-file/default/spec/custom/index.html#concepts">
+<link rel="help" href="http://www.w3.org/TR/1999/REC-xml-names-19990114/#NT-NCName">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+function composeName(charCode) {
+    return String.fromCharCode(charCode) + '-x' + charCode.toString(16);
+}
+
+// NCName definition from http://www.w3.org/TR/1999/REC-xml-names-19990114/#NT-NCName
+// NCName     ::= (Letter | '_') (NCNameChar)*
+// NCNameChar ::= Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender
+// Letter     ::= BaseChar | Ideographic
+
+test(function() {
+    testCharCode(getCharCode('_'), composeName, checkValidName);
+}, 'Registering valid custom element name starting with \'_\' char');
+
+test(function() {
+    baseCharsSingle.testEach(composeName, checkValidName);
+    baseCharsRanges.testEach(composeName, checkValidName);
+}, 'Registering valid custom element name starting with base char');
+
+test(function() {
+    ideographicCharsSingle.testEach(composeName, checkValidName);
+    ideographicCharsRanges.testEach(composeName, checkValidName);
+}, 'Registering valid custom element name starting with ideographic char');
+
+test(function() {
+    (new CharsArray(['.', '-', ':', '+', '='])).testEach(composeName, checkInvalidName);
+}, 'Registering custom element starting with invalid character (general) should fail');
+
+test(function() {
+    combiningChars.testEach(composeName, checkInvalidName);
+}, 'Registering custom element starting with invalid character (combining char) should fail');
+
+test(function() {
+    extenderChars.testEach(composeName, checkInvalidName);
+}, 'Registering custom element starting with invalid character (extender char) should fail');
+
+test(function() {
+    digitCharsRanges.testEach(composeName, checkInvalidName);
+}, 'Registering custom element starting with invalid character (digit char) should fail');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars.html b/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars.html
new file mode 100644
index 000000000..64252ab49
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-allowed-chars.html
@@ -0,0 +1,54 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Chars allowed for custom element type </title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The custom element type identifies a custom element interface and is a sequence of characters that must match the NCName production">
+<meta name="timeout" content="long">
+<link rel="help" href="https://dvcs.w3.org/hg/webcomponents/raw-file/default/spec/custom/index.html#concepts">
+<link rel="help" href="http://www.w3.org/TR/1999/REC-xml-names-19990114/#NT-NCName">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+function composeName(charCode) {
+    return 'x-' + String.fromCharCode(charCode) + '-x' + charCode.toString(16);
+}
+
+// NCName definition from http://www.w3.org/TR/1999/REC-xml-names-19990114/#NT-NCName
+// NCName     ::= (Letter | '_') (NCNameChar)*
+// NCNameChar ::= Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender
+// Letter     ::= BaseChar | Ideographic
+
+test(function() {
+    baseCharsSingle.testEach(composeName, checkValidName);
+    baseCharsRanges.testEach(composeName, checkValidName);
+}, 'Registering valid custom element types with base char');
+
+test(function() {
+    ideographicCharsSingle.testEach(composeName, checkValidName);
+    ideographicCharsRanges.testEach(composeName, checkValidName);
+}, 'Registering valid custom element types with ideographic char');
+
+test(function() {
+    digitCharsRanges.testEach(composeName, checkValidName);
+}, 'Registering valid custom element types with digit chars');
+
+test(function() {
+    (new CharsArray(['.', '-', '_'])).testEach(composeName, checkValidName)
+}, 'Registering valid custom element types with characters \'.\', \'-\', \'_\'');
+
+test(function() {
+    combiningChars.testEach(composeName, checkValidName);
+}, 'Registering valid custom element types with combining char');
+
+test(function() {
+    extenderChars.testEach(composeName, checkValidName);
+}, 'Registering valid custom element types with extender char');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-naming.html b/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-naming.html
new file mode 100644
index 000000000..c05f1ccde
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/concepts/custom-elements-type-naming.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>The custom element type is a sequence of characters that must match the NCName production and contain a minus character</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="The custom element type is a sequence of characters that must match the NCName production and contain a U+002D HYPHEN-MINUS character">
+<link rel="help" href="https://dvcs.w3.org/hg/webcomponents/raw-file/default/spec/custom/index.html#concepts">
+<link rel="help" href="http://www.w3.org/TR/1999/REC-xml-names-19990114/#NT-NCName">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var validNames = ['x-frame', 'xx-frame', 'x--frame', '_-frame', 'x-', 'x--',
+                      'x-1', 'x-_', '_-_', '__-',  '_-1',  '_-..'];
+    HTML5_ELEMENTS.forEach(function(value) {
+        validNames.push('x-' + value);
+        validNames.push('Y-' + value.toUpperCase());
+    });
+    validNames.forEach(function(value) {
+        try {
+            doc.registerElement(value);
+        } catch (e) {
+            assert_unreached('Exception should not be thrown in case of attempt ' +
+                'to register a custom element with a name \'' + value + '\'');
+        }
+    });
+}, 'Registering valid custom element types');
+
+test(function() {
+    var doc = newHTMLDocument();
+    var invalidNames = ['xframe', 'x_frame', 'x.frame', 'x1frame', '-xframe', '1-frame',
+                        '1x-frame',	'.-frame', '_frame', 'x-f!rame', 'x-:frame'];
+    invalidNames.forEach(function(value) {
+        assert_throws('SyntaxError', function() {
+            doc.registerElement(value);
+        }, 'Exception should be thrown in case of attempt to register element ' +
+            'with the name \'' + value + '\'');
+    });
+}, 'Registering invalid custom element types should fail');
+
+test(function() {
+    var doc = newHTMLDocument();
+    var forbiddenNames = ['annotation-xml',
+                        'color-profile',
+                        'font-face',
+                        'font-face-src',
+                        'font-face-uri',
+                        'font-face-format',
+                        'font-face-name',
+                        'missing-glyph'];
+    forbiddenNames.forEach(function(value) {
+        assert_throws('SyntaxError', function() {
+            doc.registerElement(value);
+        }, 'Exception should be thrown in case of attempt to register element ' +
+            'with the name \'' + value + '\'');
+    });
+}, 'Registering forbidden custom element types should fail');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/new-registry-test.html b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/new-registry-test.html
new file mode 100644
index 000000000..597f15c21
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/new-registry-test.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>When an HTML Document is loaded in a browsing context, a new registry must be created and associated with this document</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="When an HTML Document is loaded in a browsing context, a new registry must be created and associated with this document.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#creating-and-passing-registries">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+testInIFrame('../resources/blank.html', function(doc) {
+    try {
+        doc.registerElement('x-element');
+    } catch (e) {
+        assert_unreached('Unexpected exception, while registering a valid custom element');
+    }
+}, 'Document, loaded into browsing context, must have a new empty registry');
+
+
+testInIFrame('../resources/blank.html', function(loadedDocument) {
+    var createdDocument = document.implementation.createHTMLDocument('Test Document');
+    // Let's check that loadedDocument and createdDocument use different registeries.
+    createdDocument.registerElement('x-element');
+    try {
+        loadedDocument.registerElement('x-element');
+    } catch (e) {
+        assert_unreached('Unexpected exception while registering a custom element ' +
+            'in a document, which has it\'s own registry');
+    }
+}, 'Document, loaded into browsing context, must have a new empty registry, ' +
+        'which is different from other documents\' registries');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/no-registry-test.html b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/no-registry-test.html
new file mode 100644
index 000000000..d936fd34f
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/no-registry-test.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>New document without browsing context must not have a registry</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="In all other cases, new documents must not have a registry.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#creating-and-passing-registries">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = document.implementation.createDocument(null, 'test', null);
+    assert_throws(
+        'NotSupportedError',
+        function() { doc.registerElement('x-element'); },
+        'Registering valid custom element in a document ' +
+            'without registry should fail');
+}, 'Document of type other than HTML, not loaded into browsing context, must not have a registry');
+
+async_test(function(t) {
+    var request = new XMLHttpRequest();
+    request.onreadystatechange = t.step_func(function() {
+        if (request.readyState == 4){
+            assert_equals(200, request.status, 'Test document is not loaded correctly');
+            var doc = request.response;
+            assert_true(doc instanceof HTMLDocument,
+                'XMLHttpRequest\'s asynchronous response should be HTML document');
+            assert_throws(
+                'NotSupportedError',
+                function() { doc.registerElement('x-element'); },
+                'Registering valid custom element in ' +
+                    'an XMLHttpRequest\'s response document should fail');
+            t.done();
+        }
+    });
+
+    request.open('GET', '../resources/blank.html', true);
+    request.responseType = 'document';
+    request.send();
+}, 'XMLHttpRequest\'s asynchronous response HTML document must not have a registry');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-create-document.html b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-create-document.html
new file mode 100644
index 000000000..64244f169
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-create-document.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document, created with createHTMLDocument or createDocument with HTML namespace, should share registry with the associated document</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="When DOMImplementation's createDocument method is invoked with namespace set to HTML Namespace or when the createHTMLDocument method is invoked, use the registry of the associated document to the new instance.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#creating-and-passing-registries">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-frame';
+
+    var GeneratedConstructor = doc.registerElement(name);
+    var doc2 = doc.implementation.createHTMLDocument('Document 2');
+    assert_throws(
+        'NotSupportedError',
+        function() { doc2.registerElement(name); },
+        'Registering a custom element type name that is already registered in a shared ' +
+            'registry should throw an exception');
+
+    var xframe = doc2.createElement(name);
+    assert_true(xframe instanceof GeneratedConstructor,
+        'Created element should be x-frame instance');
+}, 'Document created by createHTMLDocument should share an existing registry');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-frame-1';
+
+    var GeneratedConstructor = doc.registerElement(name);
+    var doc2 = doc.implementation.createDocument(HTML_NAMESPACE, 'html', null);
+    assert_throws(
+        'NotSupportedError',
+        function() { doc2.registerElement(name); },
+        'Exception should be thrown for custom element, ' +
+            'which is already registered in shared registry');
+
+    var xframe = doc2.createElement(name);
+    assert_true(xframe instanceof GeneratedConstructor,
+        'Created element should be x-frame instance');
+}, 'Document created by createDocument with HTML namespace should share an existing registry');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-import-document.html b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-import-document.html
new file mode 100644
index 000000000..251e4f123
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/creating-and-passing-registries/share-registry-import-document.html
@@ -0,0 +1,95 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>When creating an import, use the registry of the master document</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="When creating an import, use the registry of the master document.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#creating-and-passing-registries">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+var test1 = async_test('Registry of the imported document should be shared with master document. ' +
+    'Import is asynchronous');
+test1.step(function() {
+    var iframe = newIFrame('../resources/import-master-async.html');
+    document.body.appendChild(iframe);
+    iframe.onload = test1.step_func(function() {
+        var doc = iframe.contentDocument;
+        var link = doc.querySelector('link[rel=import]');
+        link.onload = test1.step_func(function() {
+            try {
+                var doc2 = link.import;
+                var name = 'x-frame';
+                doc.registerElement(name);
+                assert_throws(
+                    'NotSupportedError',
+                    function() { doc2.registerElement(name); },
+                    'Registering a custom element type name that is already registered in a shared ' +
+                        'registry should throw an exception');
+                test1.done();
+            } finally {
+                iframe.remove();
+            }
+        });
+    });
+});
+
+
+var test2 = async_test('Registry of the master document should be shared with imported document. ' +
+    'Import is asynchronous');
+test2.step(function() {
+    var iframe = newIFrame('../resources/import-master-async.html');
+    document.body.appendChild(iframe);
+    iframe.onload = test2.step_func(function() {
+        var doc = iframe.contentDocument;
+        var link = doc.querySelector('link[rel=import]');
+        link.onload = test2.step_func(function() {
+            try {
+                var doc2 = link.import;
+                var name = 'x-frame';
+                doc2.registerElement(name);
+                assert_throws(
+                    'NotSupportedError',
+                    function() { doc.registerElement(name); },
+                    'Registering a custom element type name that is already registered in a shared ' +
+                        'registry should throw an exception');
+                test2.done();
+            } finally {
+                iframe.remove();
+            }
+        });
+    });
+});
+
+
+testInIFrame('../resources/import-master.html', function(doc) {
+    var link = doc.querySelector('link[rel=import]');
+    var doc2 = link.import;
+    var name = 'x-frame';
+    doc.registerElement(name);
+    assert_throws(
+        'NotSupportedError',
+        function() { doc2.registerElement(name); },
+        'Registering a custom element type name that is already registered in a shared ' +
+            'registry should throw an exception');
+}, 'Registry of the imported document should be shared with master document. Import is syncronous');
+
+
+testInIFrame('../resources/import-master.html', function(doc) {
+    var link = doc.querySelector('link[rel=import]');
+    var doc2 = link.import;
+    var name = 'x-frame';
+    doc2.registerElement(name);
+    assert_throws(
+        'NotSupportedError',
+        function() { doc.registerElement(name); },
+        'Registering a custom element type name that is already registered in a shared ' +
+            'registry should throw an exception');
+}, 'Registry of the master document should be shared with imported document. Import is syncronous');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/enqueuing-and-invoking-callbacks/invoke-callbacks.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/enqueuing-and-invoking-callbacks/invoke-callbacks.html
new file mode 100644
index 000000000..97fb73560
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/enqueuing-and-invoking-callbacks/invoke-callbacks.html
@@ -0,0 +1,60 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Invoke CALLBACK with ELEMENT as callback this value</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Invoke CALLBACK with ELEMENT as callback this value">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#enqueuing-and-invoking-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    doc.body.innerHTML = '<x-a id="x-a"></x-a>';
+    assert_equals(doc.querySelector('#x-a'), proto.createdCallbackThis,
+        '\'this\' value of the created callback should be the custom element');
+}, 'Test \'this\' value inside created callback.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    assert_equals(doc.querySelector('#x-element'), proto.attachedCallbackThis,
+        '\'this\' value of the attached callback should be the custom element');
+}, 'Test \'this\' value inside attached callback.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    doc.body.removeChild(customElement);
+    assert_equals(customElement, proto.detachedCallbackThis,
+        '\'this\' value of the detached callback should be the custom element');
+}, 'Test \'this\' value inside detached callback.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-b', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    customElement.setAttribute('class', 'someClass');
+    assert_equals(customElement, proto.attributeChangedCallbackThis,
+        '\'this\' value of the attributeChanged callback should be the custom element');
+}, 'Test \'this\' value inside attributeChanged callback.');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-move-element-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-move-element-test.html
new file mode 100644
index 000000000..df4df5535
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-move-element-test.html
@@ -0,0 +1,159 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Attached callback of a custom element should be called if element is moved</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="attached callback ... must be enqueued whenever custom element is inserted into a document and this document has a browsing context.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-a', {prototype: proto});
+    var customElement = doc.createElement('x-a');
+
+    doc.body.appendChild(customElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached ' +
+        'should not be called in documents that do not have a browsing context');
+
+    var divElement = doc.createElement('div');
+    doc.body.appendChild(divElement);
+    divElement.appendChild(customElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached ' +
+        'should not be called in documents that do not have a browsing context');
+}, 'Test attached callback if moving custom element inside document ' +
+    'without browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(docWithBrowsingContext) {
+    var docNoBrowsingContext = newHTMLDocument();
+    var proto1 = newHTMLElementPrototype();
+    docNoBrowsingContext.registerElement('x-b', {prototype: proto1});
+
+    var customElement = docNoBrowsingContext.createElement('x-b');
+    docNoBrowsingContext.body.appendChild(customElement);
+    assert_equals(proto1.attachedCallbackCalledCounter, 0,
+        'Callback attached should not be called ' +
+        'in documents that do not have a browsing context');
+
+    var proto2 = newHTMLElementPrototype();
+    docWithBrowsingContext.registerElement('x-b', {prototype: proto2});
+    docWithBrowsingContext.body.appendChild(customElement);
+    assert_equals(proto1.attachedCallbackCalledCounter, 1,
+        'Callback attached should be called in documents with browsing context');
+    assert_equals(proto2.attachedCallbackCalledCounter, 0,
+        'Callback attached, defined in receiving document, should not be called');
+}, 'Test attached callback if moving custom element from ' +
+    'document without browsing context to document with browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(docWithBrowsingContext) {
+    var proto1 = newHTMLElementPrototype();
+    docWithBrowsingContext.registerElement('x-c', {prototype: proto1});
+
+    var customElement = docWithBrowsingContext.createElement('x-c');
+    docWithBrowsingContext.body.appendChild(customElement);
+    assert_equals(proto1.attachedCallbackCalledCounter, 1,
+        'Callback attached should be called in documents with browsing context');
+
+    var docNoBrowsingContext = newHTMLDocument();
+    var proto2 = newHTMLElementPrototype();
+    docNoBrowsingContext.registerElement('x-c', {prototype: proto2});
+    docNoBrowsingContext.body.appendChild(customElement);
+    assert_equals(proto1.attachedCallbackCalledCounter, 1, 'Callback attached should not be called ' +
+        'in documents that do not have a browsing context');
+    assert_equals(proto2.attachedCallbackCalledCounter, 0,
+        'Callback attached, defined in receiving document, should not be called');
+}, 'Test attached callback if moving custom element from ' +
+    'document with browsing context to document without browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-d', {prototype: proto});
+
+    var customElement = doc.createElement('x-d');
+    doc.body.appendChild(customElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 1,
+        'Callback attached should be called in documents with browsing context');
+
+    var divElement = doc.createElement('div');
+    doc.body.appendChild(divElement);
+    divElement.appendChild(customElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 2,
+        'Callback attached should be called in documents with browsing context');
+}, 'Test attached callback if moving custom element inside document ' +
+    'with browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-e', {prototype: proto});
+
+    var customElement = doc.createElement('x-e');
+    doc.body.appendChild(customElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 1,
+        'Callback attached should be called in documents with browsing context');
+
+    var divElement = doc.createElement('div');
+    divElement.appendChild(customElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 1,
+        'Callback attached should not be called if element is not appended to the document');
+
+    doc.body.appendChild(divElement);
+    assert_equals(proto.attachedCallbackCalledCounter, 2,
+        'Callback attached should be called in documents with browsing context');
+}, 'Test attached callback if indirectly moving custom element inside document ' +
+    'with browsing context');
+
+
+var moveTest =  async_test('Test attached callback if moving custom element from ' +
+    'document with browsing context to document with browsing context');
+
+moveTest.step(function() {
+    var iframe1 = newIFrame('../../resources/blank.html');
+    iframe1.onload = moveTest.step_func(function() {
+        var doc1 = iframe1.contentDocument;
+
+        // register custom element type
+        var proto1 = newHTMLElementPrototype();
+        doc1.registerElement('x-f', {prototype: proto1});
+
+        // create custom element
+        var customElement = doc1.createElement('x-f');
+        doc1.body.appendChild(customElement);
+        assert_equals(proto1.attachedCallbackCalledCounter, 1,
+            'Callback attached should be called in documents with browsing context');
+
+        // create second iframe
+        var iframe2 = newIFrame('../../resources/x-element.html');
+        iframe2.onload = moveTest.step_func(function() {
+            var doc2 = iframe2.contentDocument;
+            
+            // register custom element type
+            var proto2 = newHTMLElementPrototype();
+            doc2.registerElement('x-f', {prototype: proto2});
+
+            // move element
+            doc2.body.appendChild(customElement);
+            assert_equals(proto1.attachedCallbackCalledCounter, 2,
+                'Callback attached should be called in documents with browsing context');
+            assert_equals(proto2.attachedCallbackCalledCounter, 0,
+                'Callback attached, defined in receiving document, should not be called');
+
+            // test clean up
+            iframe1.remove();
+            iframe2.remove();
+            moveTest.done();
+        });
+    });
+});
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-test.html
new file mode 100644
index 000000000..a4cc0b746
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attached-callback-test.html
@@ -0,0 +1,117 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Attached callback of a custom element should be called </title>
+<meta name="timeout" content="long">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="attached callback ... must be enqueued whenever custom element is inserted into a document and this document has a browsing context.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached ' +
+        'should not be called in documents that do not have a browsing context');
+}, 'Test attached callback if custom element is instantiated via constructor. ' +
+    'Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-b', {prototype: proto});
+    doc.body.innerHTML = '<x-b></x-b>';
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached ' +
+        'should not be called in documents that do not have a browsing context');
+}, 'Test attached callback if custom element is created via innerHTML property. ' +
+    'Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-c></x-c>';
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-c', {prototype: proto});
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached ' +
+        'should not be called in documents that do not have a browsing context');
+}, 'Test attached callback if custom element is created via innerHTML property before ' +
+    'registration. Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-d id="x-d"></x-d>';
+    var customElement = doc.querySelector('#x-d');
+
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-d', {prototype: proto});
+
+    customElement.constructor.prototype = proto;
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached should ' +
+        'not be called for unregistered custom element in document without browsing context');
+}, 'Test attached callback if custom element is unregistered');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.attachedCallbackCalledCounter, 1, 'Callback attached should be ' +
+        'called in documents with browsing context');
+}, 'Test attached callback. Document has browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var x = doc.createElement('x-element');
+    assert_equals(proto.attachedCallbackCalledCounter, 0, 'Callback attached should not ' +
+        'be called before element is added to document with browsing context');
+
+    doc.body.appendChild(x);
+    assert_equals(proto.attachedCallbackCalledCounter, 1, 'Callback attached should be called ' +
+        'in documents with browsing context');
+}, 'Test attached callback. Registered element is created via document.createElement(). ' +
+    'Document has browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var x = doc.createElement('x-element');
+    doc.body.appendChild(x);
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.attachedCallbackCalledCounter, 1, 'Callback attached should ' +
+        'be called in documents with browsing context');
+}, 'Test attached callback. Unregistered element is created via document.createElement(). ' +
+    'Document has browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    doc.body.innerHTML = '<x-element></x-element>';
+    assert_equals(proto.attachedCallbackCalledCounter, 1, 'Callback attached should ' +
+        'be called in documents with browsing context');
+}, 'Test attached callback. Registered element is created via innerHTML property. ' +
+    'Document has browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    doc.body.innerHTML = '<x-element></x-element>';
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.attachedCallbackCalledCounter, 1, 'Callback attached should ' +
+        'be called in documents with browsing context');
+}, 'Test attached callback. Unresolved element is created via innerHTML property. ' +
+    'Document has browsing context');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-change-attribute-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-change-attribute-test.html
new file mode 100644
index 000000000..cd5f3a4b8
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-change-attribute-test.html
@@ -0,0 +1,229 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Test attributeChanged callback is called if custom element attribute value is changed</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="attributeChanged callback must be enqueued whenever custom element's attribute is added, changed or removed">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    customElement.setAttribute('class', 'someClass');
+    proto.attributeChangedCallbackCalledCounter = 0;
+    customElement.setAttribute('class', 'someClass2');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is changed by method ' +
+    'setAttribute(). The custom element is created via constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-b', {prototype: proto});
+
+    doc.body.innerHTML = '<x-b id="x-b" class="oldValue"></x-b>';
+    var customElement = doc.querySelector('#x-b');
+    customElement.setAttribute('class', 'newValue');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'oldValue', 'newValue'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is changed by method ' +
+    'setAttribute(). The custom element is created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-c', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    customElement.setAttribute('class', 'someClass');
+    proto.attributeChangedCallbackCalledCounter = 0;
+    customElement.classList.add('someClass3');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is changed by method ' +
+    'classList.add(). The custom element is created via constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-d', {prototype: proto});
+
+    doc.body.innerHTML = '<x-d id="x-d" class="oldValue"></x-d>';
+    var customElement = doc.querySelector('#x-d');
+    customElement.classList.add('newestValue');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'oldValue', 'oldValue newestValue'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is changed by method ' +
+    'classList.add(). The custom element is created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-e', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    customElement.setAttribute('class', 'someClass');
+    proto.attributeChangedCallbackCalledCounter = 0;
+    customElement.id = 'someId';
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is changed as property. ' +
+    'The custom element is created via constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-f', {prototype: proto});
+
+    doc.body.innerHTML = '<x-f id="x-f" class="oldValue"></x-f>';
+    var customElement = doc.querySelector('#x-f');
+    customElement.className = 'lastValue';
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'oldValue', 'lastValue'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is changed as property. ' +
+    'The custom element is created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-g', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    customElement.setAttribute('class', 'someClass someSuperClass');
+    proto.attributeChangedCallbackCalledCounter = 0;
+    customElement.classList.toggle('someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is changed by classList.toggle(). ' +
+    'The custom element is created via constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-h', {prototype: proto});
+
+    doc.body.innerHTML = '<x-h id="x-h" class="oldValue lastValue"></x-h>';
+    var customElement = doc.querySelector('#x-h');
+    customElement.classList.toggle('lastValue');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'oldValue lastValue', 'oldValue'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is changed by classList.toggle(). ' +
+    'The custom element is created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-i id="x-i" class="oldValue"></x-i>';
+    var customElement = doc.querySelector('#x-i');
+    customElement.setAttribute('class', 'newValue');
+    customElement.setAttribute('class', 'newestValue');
+
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-i', {prototype: proto});
+
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 0,
+        'Callback attributeChanged should not be called');
+
+    customElement.setAttribute('class', 'rightValue');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should not be called');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'newestValue', 'rightValue'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback is not called if custom element is not registered');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('class', 'firstValue');
+    customElement.setAttribute('class', 'secondValue');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 2, 'Callback ' +
+        'attributeChanged should be called after call to setAttribute()');
+
+    customElement.classList.add('someClass3');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 3, 'Callback ' +
+        'attributeChanged should be called after call to classList.add()');
+
+    customElement.id = 'someId';
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 4, 'Callback ' +
+        'attributeChanged should be called after changing attribute as property');
+}, 'Test attributeChanged callback is called if attribute value is changed. ' +
+    'The document has browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    var customElement = doc.querySelector('#x-element');
+
+    customElement.setAttribute('class', 'firstValue');
+    customElement.setAttribute('class', 'secondValue');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'firstValue', 'secondValue'],
+        'Unexpected callback attributeChanged arguments after call to setAttribute()');
+
+    customElement.classList.add('newestValue');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'secondValue', 'secondValue newestValue'],
+        'Unexpected callback attributeChanged arguments after call to classList.add()');
+
+    customElement.className = 'lastValue';
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'secondValue newestValue', 'lastValue'],
+        'Unexpected callback attributeChanged arguments after changing attribute as property');
+}, 'Test attributeChanged callback arguments if attribute value is changed. ' +
+    'The document has browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('class', 'firstValue');
+    customElement.setAttribute('class', 'secondValue');
+
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    customElement.setAttribute('class', 'thirdValue');
+
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+    assert_array_equals(proto.attributeChangedCallbackArgs,
+        ['class', 'secondValue', 'thirdValue'],
+        'Unexpected callback attributeChanged arguments after setAttribute() call');
+}, 'Test attributeChanged callback is not called if custom element is not registered. ' +
+    'The document has browsing context');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-remove-attribute-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-remove-attribute-test.html
new file mode 100644
index 000000000..fb451b074
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-remove-attribute-test.html
@@ -0,0 +1,166 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Test attribute removing to check attributeChanged callback of a custom element</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="attributeChanged callback must be enqueued whenever custom element's attribute is removed">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    //attributeChangedCallback should be called the first time here
+    customElement.setAttribute('class', 'someClass');
+    //attributeChangedCallback should be called the second time here
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 2, 'Callback attributeChanged should be called ' +
+        'after setAttribute() and removeAttribute() calls');
+}, 'Test attributeChanged callback if attribute is removed. ' +
+    'The custom element created via constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(element) {
+        var obj = doc.createElement(element);
+        var proto = newCustomElementPrototype(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement('x-' + element + '-' + element + '-1', {
+            prototype: proto,
+            extends: element
+        });
+
+        var customElement = new GeneratedConstructor();
+        //attributeChangedCallback should be called the first time here
+        customElement.setAttribute('class', 'someClass');
+        //attributeChangedCallback should be called the second time here
+        customElement.removeAttribute('class');
+        assert_equals(proto.attributeChangedCallbackCalledCounter, 2, 
+            'Callback attributeChanged should be called ' +
+            'after setAttribute() and removeAttribute() calls for "' + element + '"');
+    });
+}, 'Test attributeChanged callback if attribute is removed. ' +
+    'The custom element created via constructor and extends HTML element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-b', {prototype: proto});
+
+    doc.body.innerHTML = '<x-b id="x-b" class="theClass"></x-b>';
+    var customElement = doc.querySelector('#x-b');
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called ' +
+        'after removeAttribute() call');
+}, 'Test attributeChanged callback if attribute is removed. ' +
+    'The custom element created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-c', {prototype: proto});
+
+    doc.body.innerHTML = '<x-c id="x-c" class="theClass"></x-c>';
+    var customElement = doc.querySelector('#x-c');
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackArgs[2], null, 
+        'Removing an attribute should invoke ' +
+        'the attributeChanged callback with a null new value');
+    assert_array_equals(proto.attributeChangedCallbackArgs, 
+        ['class', 'theClass', null],
+        'Unexpected attributeChanged callback arguments');
+}, 'Test attributeChanged callback arguments if attribute is removed. ' +
+    'The custom element created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.body.innerHTML = '<x-d id="x-d" class="theClass"></x-d>';
+    var customElement = doc.querySelector('#x-d');
+    // this should not call or enqueue attributeChangedCallback
+    customElement.setAttribute('class', 'someClass');
+    // this one should not too
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 0, 
+        'Callback attributeChanged should not be called');
+
+    doc.registerElement('x-d', {prototype: proto});
+    // this call invokes attributeChangedCallback
+    customElement.setAttribute('name', 'someName');
+    // and this one
+    customElement.removeAttribute('name');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 2, 
+        'Callback attributeChanged should be called ' +
+        'after setAttribute() and removeAttribute() calls');
+}, 'Test attributeChanged callback is not called if attribute is removed. ' +
+    'The custom element created via innerHTML property and unresolved at first');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('class', 'someClass');
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 2, 
+        'Callback attributeChanged should be called ' +
+        'after setAttribute() and removeAttribute() calls');
+}, 'Test attributeChanged callback is called if attribute is removed. ' +
+    'The custom element created via constructor and the document has browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    doc.body.innerHTML = '<x-element id="x-element" class="theClass"></x-element>';
+    var customElement = doc.querySelector('#x-element');
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackArgs[2], null, 
+        'Removing an attribute should invoke ' +
+        'the attributeChanged callback with a null new value');
+    assert_array_equals(proto.attributeChangedCallbackArgs, 
+        ['class', 'theClass', null],
+        'Unexpected attributeChanged callback arguments');
+}, 'Test attributeChanged callback arguments if attribute is removed. ' +
+    'The custom element created via innerHTML property and the document has browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var customElement = doc.querySelector('#x-element');
+    // this should not call or enqueue attributeChangedCallback
+    customElement.setAttribute('name', 'someName');
+    // this one too
+    customElement.removeAttribute('name');
+
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 0, 
+        'Callback attributeChanged should not be called');
+    // this call invokes attributeChangedCallback
+    customElement.setAttribute('class', 'someClass');
+    // this call invokes attributeChangedCallback at second time
+    customElement.removeAttribute('class');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 2, 
+        'Callback attributeChanged should be called ' +
+        'after setAttribute() and removeAttribute() calls');
+}, 'Test attributeChanged callback if attribute is removed. ' +
+    'The custom element created via innerHTML property and unresolved at first. ' +
+    'The document has browsing context');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-set-attribute-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-set-attribute-test.html
new file mode 100644
index 000000000..1c4ab8618
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/attribute-changed-callback-set-attribute-test.html
@@ -0,0 +1,338 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Test attributeChanged callback is called if custom element attribute value is set</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="attributeChanged callback ... must be enqueued whenever custom element's attribute is added, changed or removed.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.setAttribute('class', 'someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set by method ' +
+    'setAttribute(). The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-b', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.setAttribute('class', 'someClass');
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set by method ' +
+    'setAttribute(). The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-c', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.classList.add('someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set by method ' +
+    'classList.add(). The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-d', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.classList.add('someClass');
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set by method ' +
+    'classList.add(). The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-e', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.classList.toggle('someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set by method ' +
+    'classList.toggle(). The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-f', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.classList.toggle('someClass');
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set by method ' +
+    'classList.toggle(). The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-g', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.className = 'someClass';
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1,
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set as property. ' +
+    'The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-h', {prototype: proto});
+
+    var customElement = new GeneratedConstructor();
+    customElement.className = 'someClass';
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set as property. '+
+    'The custom element is created via constructor.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-i', {prototype: proto});
+
+    doc.body.innerHTML = '<x-i id="x-i" class="theClass"></x-i>';
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 0, 
+        'Callback attributeChanged should not be called');
+}, 'Test attributeChanged callback is not called if attribute value is specified in HTML. '+
+    'The custom element is created via innerHTML property.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-j', {prototype: proto});
+
+    doc.body.innerHTML = '<x-j id="x-j" class="theClass"></x-j>';
+    var customElement = doc.querySelector('#x-j');
+    customElement.setAttribute('class', 'someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set by method setAttribute(). '+
+    'The custom element is created via innerHTML property.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-k', {prototype: proto});
+
+    doc.body.innerHTML = '<x-k id="x-k"></x-k>';
+    var customElement = doc.querySelector('#x-k');
+    customElement.setAttribute('class', 'someClass');
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set by method setAttribute(). '+
+    'The custom element is created via innerHTML property.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+
+    doc.body.innerHTML = '<x-l id="x-l"></x-l>';
+    var customElement = doc.querySelector('#x-l');
+    // this call shouldn't invoke or enqueue the callback
+    customElement.setAttribute('class', 'someClass');
+
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-l', {prototype: proto});
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 0, 
+        'Callback attributeChanged should not be called');
+    // this one should
+    customElement.setAttribute('class', 'someClass2');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is not called if attribute value of unresolved element '+
+    'is set by method setAttribute().');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(element) {
+        var obj = doc.createElement(element);
+        var proto = newCustomElementPrototype(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement('x-' + element + '-' + element + '-1', {
+            prototype: proto,
+            extends: element
+        });
+
+        var customElement = new GeneratedConstructor();
+        customElement.setAttribute('class', 'someClass');
+        assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+            'Callback attributeChanged should be called');
+    });
+}, 'Test attributeChanged callback of the custom element that extends some HTML element. ' +
+    'Test that the callback is called');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(element) {
+        var obj = doc.createElement(element);
+        var proto = newCustomElementPrototype(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement('x-' + element + '-' + element + '-1-1', {
+            prototype: proto,
+            extends: element
+        });
+
+        var customElement = new GeneratedConstructor();
+        customElement.classList.add('someClass');
+        assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+            'Callback attributeChanged should be called');
+    });
+}, 'Test attributeChanged callback is called if attribute is set by method classList.add(). '+
+    'The custom element extends some HTML element.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(element) {
+        var obj = doc.createElement(element);
+        var proto = newCustomElementPrototype(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement('x-' + element + '-' + element + '-2', {
+            prototype: proto,
+            extends: element
+        });
+
+        var customElement = new GeneratedConstructor();
+        customElement.setAttribute('class', 'someClass');
+        assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+            'Unexpected callback attributeChanged arguments');
+    });
+}, 'Test attributeChanged callback arguments if attribute value is set by method setAttribute(). '+
+    'The custom element extends some HTML element.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('class', 'someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set by method setAttribute(). '+
+    'The document has browsing context.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('class', 'someClass');
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set by method setAttribute(). '+
+    'The document has browsing context.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    customElement.classList.add('someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is called if attribute value is set by method classList.add(). '+
+    'The document has browsing context.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+
+    var customElement = doc.querySelector('#x-element');
+    customElement.classList.add('someClass');
+    assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+        'Unexpected callback attributeChanged arguments');
+}, 'Test attributeChanged callback arguments if attribute value is set by method classList.add(). '+
+    'The document has browsing context.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var customElement = doc.querySelector('#x-element');
+    // this call shouldn't invoke or enqueue the callback
+    customElement.setAttribute('name', 'someName');
+
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 0, 
+        'Callback attributeChanged should not be called');
+    // this one should
+    customElement.setAttribute('class', 'someClass');
+    assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+        'Callback attributeChanged should be called');
+}, 'Test attributeChanged callback is not called if attribute value of unresolved element '+
+    'is set by method setAttribute(). The document has browsing context.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    HTML5_ELEMENTS.forEach(function(element) {
+        var obj = doc.createElement(element);
+        var proto = newCustomElementPrototype(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement('x-' + element + '-' + element + '-1', {
+            prototype: proto,
+            extends: element
+        });
+
+        var customElement = new GeneratedConstructor();
+        customElement.setAttribute('class', 'someClass');
+        assert_equals(proto.attributeChangedCallbackCalledCounter, 1, 
+            'Callback attributeChanged should be called');
+    });
+}, 'Test attributeChanged callback is called if attribute value is set by method setAttribute(). '+
+    'The document has browsing context. The custom element extends some HTML element.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    HTML5_ELEMENTS.forEach(function(element) {
+        var obj = doc.createElement(element);
+        var proto = newCustomElementPrototype(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement('x-' + element + '-' + element + '-2', {
+            prototype: proto,
+            extends: element
+        });
+
+        var customElement = new GeneratedConstructor();
+        customElement.setAttribute('class', 'someClass');
+        assert_array_equals(proto.attributeChangedCallbackArgs, ['class', null, 'someClass'],
+            'Unexpected callback attributeChanged arguments');
+    });
+}, 'Test attributeChanged callback arguments if attribute value is set by method setAttribute(). '+
+    'The document has browsing context. The custom element extends some HTML element.');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-element-prototype-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-element-prototype-test.html
new file mode 100644
index 000000000..188957c1a
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-element-prototype-test.html
@@ -0,0 +1,87 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>The custom element prototype must be set just prior to invoking created callback</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="The custom element prototype must be set just prior to invoking callback.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.body.innerHTML = '<x-a></x-a>';
+    doc.registerElement('x-a', {prototype: proto});
+    assert_equals(proto.createdCallbackThis.constructor.prototype, proto,
+        'The custom element prototype is incorrect inside created callback');
+}, 'Test custom element prototype inside created callback when custom element is created ' +
+    'in HTML before registration of a custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.registerElement('x-b', {prototype: proto});
+    doc.body.innerHTML = '<x-b></x-b>';
+    assert_equals(proto.createdCallbackThis.constructor.prototype, proto,
+        'The custom element prototype is incorrect inside created callback');
+}, 'Test custom element prototype inside created callback when custom element is created ' +
+    'in HTML after registration of a custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var customElement = doc.createElement('x-c');
+
+    doc.body.appendChild(customElement);
+    doc.registerElement('x-c', {prototype: proto});
+    assert_equals(proto.createdCallbackThis.constructor.prototype, proto,
+        'The custom element prototype is incorrect inside created callback');
+}, 'Test custom element prototype inside created callback when custom element is created ' +
+    'via document.createElement() before registration of a custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-d', {prototype: proto});
+
+    var customElement = doc.createElement('x-d');
+    doc.body.appendChild(customElement);
+    assert_equals(proto.createdCallbackThis.constructor.prototype, proto,
+        'The custom element prototype is incorrect inside created callback');
+}, 'Test custom element prototype inside created callback when custom element is created ' +
+    'via document.createElement() after registration of a custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-e', {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    assert_equals(proto.createdCallbackThis.constructor.prototype, proto,
+        'The custom element prototype is incorrect inside created callback');
+}, 'Test custom element prototype inside created callback when custom element is created ' +
+    'via constructor returned by method registerElement');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.createdCallbackThis.constructor.prototype, proto,
+        'The custom element prototype is incorrect inside created callback');
+}, 'Test custom element prototype inside created callback when custom element is created ' +
+    'by UA parser before registration of a custom element');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-order-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-order-test.html
new file mode 100644
index 000000000..b0f2d5ee8
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-order-test.html
@@ -0,0 +1,242 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>All other callbacks must not be enqueued until after the created callback's invocation had started</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="All other callbacks must not be enqueued until after the created callback's invocation had started.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+function newPrototypeWithCallbackLog() {
+    var proto = Object.create(HTMLElement.prototype);
+    proto.callbackLog = [];
+    proto.createdCallback = function() {
+        proto.callbackLog.push('created');
+    };
+    proto.attachedCallback = function() {
+        proto.callbackLog.push('attached');
+    };
+    proto.attributeChangedCallback = function() {
+        proto.callbackLog.push('attributeChanged');
+    };
+    proto.detachedCallback = function() {
+        proto.callbackLog.push('detached');
+    };
+    return proto;
+}
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newPrototypeWithCallbackLog();
+    doc.registerElement('x-a', {prototype: proto});
+    doc.body.innerHTML = '<x-a></x-a>';
+
+    assert_equals(proto.callbackLog[0], 'created', 'The callback ' +
+        proto.callbackLog[0] + ' should be enqueued after created callback');
+    assert_in_array('attached', proto.callbackLog, 'The callback ' +
+        'attached should be called');
+}, 'Test attached callback is enqueued after created callback');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newPrototypeWithCallbackLog();
+    doc.registerElement('x-b', {prototype: proto});
+    doc.body.innerHTML = '<x-b id="x-b"></x-b>';
+    var customElement = doc.querySelector('#x-b');
+    customElement.setAttribute('key', 'value');
+
+    assert_equals(proto.callbackLog[0], 'created', 'The callback ' +
+        proto.callbackLog[0] + ' should not be enqueued before created callback');
+    assert_in_array('attributeChanged', proto.callbackLog,
+        'The callback attributeChanged should be called');
+}, 'Test attributeChanged callback is enqueued after created callback. ' +
+    'Document has browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newPrototypeWithCallbackLog();
+    doc.registerElement('x-c', {prototype: proto});
+    doc.body.innerHTML = '<x-c id="x-c"></x-c>';
+    var customElement = doc.querySelector('#x-c');
+    customElement.setAttribute('key', 'value');
+    assert_equals(proto.callbackLog[0], 'created', 'The callback ' +
+        proto.callbackLog[0] + ' should not be enqueued before created callback');
+    assert_in_array('attributeChanged', proto.callbackLog,
+        'The callback attributeChanged should be called');
+}, 'Test attributeChanged callback is enqueued after created callback. ' +
+    'Document has no browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newPrototypeWithCallbackLog();
+    doc.registerElement('x-element', {prototype: proto});
+    var customElement = doc.querySelector('#x-element');
+    doc.body.removeChild(customElement);
+
+    assert_equals(proto.callbackLog[0], 'created', 'The callback ' +
+        proto.callbackLog[0] + ' should not be enqueued before created callback');
+    assert_in_array('detached', proto.callbackLog,
+        'The callback detached should be called');
+}, 'Test detached callback is enqueued after created callback.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto1 = newPrototypeWithCallbackLog();
+    proto1.createdCallback = function() {
+        proto1.callbackLog.push('created');
+        var xe = doc.querySelector('#x-e');
+        xe.setAttribute('key', 'value');
+    };
+    var proto2 = newPrototypeWithCallbackLog();
+
+    doc.registerElement('x-d', {prototype: proto1});
+    doc.registerElement('x-e', {prototype: proto2});
+    doc.body.innerHTML = '<x-d><x-e id="x-e"></x-e></x-d>';
+
+    assert_array_equals(proto2.callbackLog, ['created'],
+        'attributeChanged callback should not be enqueued before created callback');
+}, 'Test attributeChanged callback is not enqueued before created callback started. ' +
+    'Document has no browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto1 = newPrototypeWithCallbackLog();
+    proto1.createdCallback = function() {
+        proto1.callbackLog.push('created');
+        var xe = doc.querySelector('#x-g');
+        xe.setAttribute('key', 'value');
+    };
+    var proto2 = newPrototypeWithCallbackLog();
+
+    doc.registerElement('x-f', {prototype: proto1});
+    doc.registerElement('x-g', {prototype: proto2});
+    doc.body.innerHTML = '<x-f><x-g id="x-g"></x-g></x-f>';
+
+    assert_array_equals(proto2.callbackLog, ['created', 'attached'],
+        'attributeChanged callback should not be called before created callback started');
+}, 'Test attributeChanged callback is not enqueued before created callback started. ' +
+    'Document has browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newPrototypeWithCallbackLog();
+    proto.createdCallback = function() {
+        proto.callbackLog.push('created');
+        this.setAttribute('key', 'value');
+    };
+    doc.registerElement('x-h', {prototype: proto});
+    doc.body.innerHTML = '<x-h></x-h>';
+
+    assert_array_equals(proto.callbackLog, ['created', 'attributeChanged'],
+        'attributeChanged callback should be enqueued after created callback');
+}, 'Test attributeChanged callback is enqueued after created callback started. ' +
+    'Document has no browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(docWithBrowsingContext) {
+    var docNoBrowsingContext = newHTMLDocument();
+
+    var proto1 = newPrototypeWithCallbackLog();
+    var proto2 = newPrototypeWithCallbackLog();
+    proto1.createdCallback = function() {
+        proto1.callbackLog.push('created');
+        var xk = docNoBrowsingContext.querySelector('#x-k');
+        assert_equals(proto2.callbackLog.length, 0, 'Created callback for x-k ' +
+            'should not be called before created callback for x-i');
+        docWithBrowsingContext.body.appendChild(xk);
+    };
+
+    docNoBrowsingContext.registerElement('x-i', {prototype: proto1});
+    docNoBrowsingContext.registerElement('x-k', {prototype: proto2});
+    docNoBrowsingContext.body.innerHTML = '<x-i><x-k id="x-k"></x-k></x-i>';
+
+    // Though at the moment of inserting <x-k> into docWithBrowsingContext
+    // created callback is not called for <x-k> yet, attached calback is enqueued
+    // anyway. Because specification for setting custom element prototype algorithm reads:
+    //  ....
+    //   3. If ELEMENT is in a document and this document has a browsing context:
+    //       1. Enqueue attached callback for ELEMENT
+    //
+    // Changes in the specification will follow, to reflect this exceptional case.
+    assert_array_equals(proto2.callbackLog, ['created', 'attached'],
+        'attached callback should be enqueued when custom element prototype is set');
+}, 'Test attached callback is enqueued after created callback, but before created callback had started');
+
+
+testInIFrame('../../resources/blank.html', function(docWithBrowsingContext) {
+    var docNoBrowsingContext = newHTMLDocument();
+
+    var proto = newPrototypeWithCallbackLog();
+    proto.createdCallback = function() {
+        proto.callbackLog.push('created');
+        docWithBrowsingContext.body.appendChild(this);
+    };
+
+    docNoBrowsingContext.registerElement('x-l', {prototype: proto});
+    docNoBrowsingContext.body.innerHTML = '<x-l></x-l>';
+    assert_array_equals(proto.callbackLog, ['created', 'attached'],
+        'attached callback should be enqueued after created callback had started');
+}, 'Test attached callback is enqueued after created callback had started');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto1 = newPrototypeWithCallbackLog();
+    var proto2 = newPrototypeWithCallbackLog();
+    proto1.createdCallback = function() {
+        proto1.callbackLog.push('created');
+        var xn = doc.querySelector('#x-n');
+        assert_equals(proto2.callbackLog.length, 0, 'Created callback for x-n ' +
+            'should not be called before created callback for x-m');
+        this.removeChild(xn);
+    };
+
+    doc.registerElement('x-m', {prototype: proto1});
+    doc.registerElement('x-n', {prototype: proto2});
+    doc.body.innerHTML = '<x-m><x-n id="x-n"></x-n></x-m>';
+    assert_array_equals(proto2.callbackLog, ['created'],
+        'detached callback should not be enqueued before created callback had started');
+}, 'Test detached callback is not enqueued before created callback had started');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newPrototypeWithCallbackLog();
+    proto.createdCallback = function() {
+        proto.callbackLog.push('created');
+        this.remove();
+    };
+
+    doc.registerElement('x-o', {prototype: proto});
+    doc.body.innerHTML = '<x-o></x-o>';
+
+    assert_array_equals(proto.callbackLog, ['created', 'attached', 'detached'],
+        'detached callback should be enqueued after created callback had started');
+}, 'Test detached callback is enqueued after created callback had started');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newPrototypeWithCallbackLog();
+    doc.registerElement('x-element', {prototype: proto});
+
+    // Though at the moment of inserting <x-element> into the document
+    // created callback is not called for <x-element> yet, attached calback is enqueued
+    // anyway. Because specification for setting custom element prototype algorithm reads:
+    //  ....
+    //   3. If ELEMENT is in a document and this document has a browsing context:
+    //       1. Enqueue attached callback for ELEMENT
+    //
+    // Changes in the specification will follow, to reflect this exceptional case.
+    assert_array_equals(proto.callbackLog, ['created', 'attached'],
+        'attached callback should be enqueued when custom element prototype is set');
+}, 'Test attached callback is enqueued after created callback after registration ' +
+    'of custom element type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-test.html
new file mode 100644
index 000000000..63814a80f
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/created-callback-invocation-test.html
@@ -0,0 +1,167 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Created callback of a custom element should be invoked after custom element instance is created and its definition is registered</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="CREATED callback is invoked after custom element instance is created and its definition is registered">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Callback created should not be called before element instance was created');
+    var customElement = new GeneratedConstructor();
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback when custom element is created by constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-b', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Callback created should not be called before element instance was created');
+    doc.body.innerHTML = '<x-b></x-b>';
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback when custom element is created in HTML');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-c', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Callback created should not be called before element instance was created');
+    doc.body.innerHTML = '<div><x-c></x-c></div>';
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback when custom element is created in HTML as descendant of ' +
+    'another element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-d', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Callback created should not be called before element instance was created');
+    var customElement = doc.createElement('x-d');
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback when custom element is created by createElement');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.body.innerHTML = '<x-e></x-e>';
+    doc.registerElement('x-e', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback when custom element is created in HTML before ' +
+    'registration of a custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-f', {prototype: proto});
+    doc.body.innerHTML = '<x-f-unresolved id="x-f-unresolved"></x-f-unresolved>';
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Callback created should not be called if custom element is unresolved');
+
+    var customElement = doc.querySelector('#x-f-unresolved');
+    customElement.constructor.prototype = proto;
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Created callback should not be called if custom element is unresolved');
+}, 'Test created callback if custom element is unresolved.');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 1, 'Callback created should be called');
+}, 'Test created callback is called after custom element is created and registered. ' +
+    'Document has browsing context');
+
+
+testInIFrame('../../resources/register-and-create-custom-element.html', function(doc) {
+    assert_equals(doc.querySelector('#log').textContent, 'Created callback was called',
+        'Callback created should be called');
+}, 'Test created callback is called after custom element is registered and created. ' +
+    'Document has browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var customElement = doc.createElement('x-g');
+
+    doc.registerElement('x-g', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after registration of custom element');
+}, 'Test created callback when custom element is created by createElement '+
+    'before registration of a custom element');
+
+
+test(function(){
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var GeneratedConstructor = doc.registerElement('x-h', {prototype: proto});
+
+    var customElement1 = new GeneratedConstructor();
+    assert_equals(proto.createdCallbackCalledCounter, 1, 'Callback created should be called');
+
+    var customElement2 = doc.createElement('x-h');
+    assert_equals(proto.createdCallbackCalledCounter, 2,
+        'Callback created should be called after element instance was created');
+
+    doc.body.innerHTML = '<x-h></x-h>';
+    assert_equals(proto.createdCallbackCalledCounter, 3,
+        'Callback created should be called after element instance was created');
+
+    doc.body.innerHTML = '<div><x-h></x-h></div>';
+    assert_equals(proto.createdCallbackCalledCounter, 4,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback. Create several custom elements using different ways');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+
+    var GeneratedConstructor = doc.registerElement('x-element', {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called for custom element in loaded document');
+
+    var customElement2 = new GeneratedConstructor();
+    assert_equals(proto.createdCallbackCalledCounter, 2,
+        'Callback created should be called after element instance was created');
+
+    var customElement3 = doc.createElement('x-element');
+    assert_equals(proto.createdCallbackCalledCounter, 3,
+        'Callback created should be called after element instance was created');
+
+    doc.body.innerHTML = '<x-element></x-element>';
+    assert_equals(proto.createdCallbackCalledCounter, 4,
+        'Callback created should be called after element instance was created');
+
+    doc.body.innerHTML = '<div><x-element></x-element></div>';
+    assert_equals(proto.createdCallbackCalledCounter, 5,
+        'Callback created should be called after element instance was created');
+}, 'Test created callback. Create several custom elements using different ways. ' +
+    'Document has browsing context');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-move-element-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-move-element-test.html
new file mode 100644
index 000000000..d69eb54db
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-move-element-test.html
@@ -0,0 +1,130 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Test detached callback of a custom element when moving custom element between different documents</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="detached callback ... must be enqueued whenever custom element is removed from the document and this document has a browsing context.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-a', {prototype: proto});
+
+    var customElement = doc.createElement('x-a');
+    doc.body.appendChild(customElement);
+
+    var divElement = doc.createElement('div');
+    doc.body.appendChild(divElement);
+    divElement.appendChild(customElement);
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called in document without a browsing context');
+}, 'Test detached callback is not called if moving custom element inside document ' +
+    'without browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(docWithBrowsingContext) {
+    var docNoBrowsingContext = newHTMLDocument();
+    var proto1 = newHTMLElementPrototype();
+    docNoBrowsingContext.registerElement('x-b', {prototype: proto1});
+
+    var customElement = docNoBrowsingContext.createElement('x-b');
+    docNoBrowsingContext.body.appendChild(customElement);
+    var proto2 = newHTMLElementPrototype();
+    docWithBrowsingContext.registerElement('x-b', {prototype: proto2});
+    docWithBrowsingContext.body.appendChild(customElement);
+
+    assert_equals(proto1.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called in document without browsing context');
+    assert_equals(proto2.detachedCallbackCalledCounter, 0,
+        'Callback detached, defined in receiving document, should not be called');
+}, 'Test detached callback is not called if moving custom element from ' +
+    'document without browsing context to document with browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(docWithBrowsingContext) {
+    var proto1 = newHTMLElementPrototype();
+    docWithBrowsingContext.registerElement('x-c', {prototype: proto1});
+
+    var customElement = docWithBrowsingContext.createElement('x-c');
+    docWithBrowsingContext.body.appendChild(customElement);
+
+    var docNoBrowsingContext = newHTMLDocument();
+    var proto2 = newHTMLElementPrototype();
+    docNoBrowsingContext.registerElement('x-c', {prototype: proto2});
+    docNoBrowsingContext.body.appendChild(customElement);
+    assert_equals(proto1.detachedCallbackCalledCounter, 1,
+        'Callback detached should be called in documents with browsing context');
+    assert_equals(proto2.detachedCallbackCalledCounter, 0,
+        'Callback detached, defined in receiving document, should not be called');
+}, 'Test detached callback if moving custom element from ' +
+    'document with browsing context to document without browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-d', {prototype: proto});
+
+    var customElement = doc.createElement('x-d');
+    doc.body.appendChild(customElement);
+    var divElement = doc.createElement('div');
+    doc.body.appendChild(divElement);
+    divElement.appendChild(customElement);
+    assert_equals(proto.detachedCallbackCalledCounter, 1,
+        'Callback detached should be called in documents with browsing context');
+}, 'Test detached callback if moving custom element inside document ' +
+    'with browsing context');
+
+
+var moveTest =  async_test('Test detached callback if moving custom element from ' +
+    'document with browsing context to document with browsing context');
+
+moveTest.step(function() {
+    var iframe1 = newIFrame('../../resources/blank.html');
+    iframe1.onload = moveTest.step_func(function() {
+        var doc1 = iframe1.contentDocument;
+
+        // register custom element type
+        var proto1 = newHTMLElementPrototype();
+        doc1.registerElement('x-e', {prototype: proto1});
+
+        // create custom element
+        var customElement = doc1.createElement('x-e');
+        doc1.body.appendChild(customElement);
+        assert_equals(proto1.detachedCallbackCalledCounter, 0,
+            'Callback detached should not be called when element is created');
+
+        // create second iframe
+        var iframe2 = newIFrame('../../resources/x-element.html');
+        iframe2.onload = moveTest.step_func(function() {
+            var doc2 = iframe2.contentDocument;
+
+            // register custom element type
+            var proto2 = newHTMLElementPrototype();
+            doc2.registerElement('x-e', {prototype: proto2});
+
+            // move element
+            doc2.body.appendChild(customElement);
+            assert_equals(proto1.detachedCallbackCalledCounter, 1,
+                'Callback detached should be called in documents with browsing context');
+            assert_equals(proto2.detachedCallbackCalledCounter, 0,
+                'Callback detached, defined in receiving document, should not be called');
+
+            // test clean up
+            iframe1.remove();
+            iframe2.remove();
+            moveTest.done();
+        });
+
+    });
+});
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-no-browsing-context-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-no-browsing-context-test.html
new file mode 100644
index 000000000..2b420d11c
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-no-browsing-context-test.html
@@ -0,0 +1,147 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Detached callback of a custom element should not be called if document has no browsing context</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="detached callback ... must be enqueued whenever custom element is removed from the document and this document has a browsing context.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-a', {prototype: proto});
+    doc.body.innerHTML = '<x-a id="x-a"></x-a>';
+    var customElement = doc.querySelector('#x-a');
+    doc.body.removeChild(customElement);
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called if the document has no browsing context');
+}, 'Test detached callback if custom element is created via innerHTML property. ' +
+    'Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    doc.body.innerHTML = '<x-b id="x-b"></x-b>';
+    doc.registerElement('x-b', {prototype: proto});
+    var customElement = doc.querySelector('#x-b');
+    doc.body.removeChild(customElement);
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called if the document has no browsing context');
+}, 'Test detached callback if custom element is via innerHTML property before ' +
+    'registration of a custom element. Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-c id="x-c"></x-c>';
+    var customElement = doc.querySelector('#x-c');
+
+    var proto = newHTMLElementPrototype();
+    customElement.constructor.prototype = proto;
+    doc.body.removeChild(customElement);
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called if the document has no browsing context');
+}, 'Test detached callback if custom element is unregistered. ' +
+    'Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.registerElement('x-d', {prototype: proto});
+    doc.body.innerHTML = '<x-d id="x-d"></x-d>';
+    doc.body.innerHTML = '';
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called if the document has no browsing context');
+}, 'Test detached callback if removing custom element via innerHTML property. ' +
+    'Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.registerElement('x-e', {prototype: proto});
+    doc.body.innerHTML = '<div id="customParent"><x-e id="x-e"></x-e></div>';
+    var parent = doc.querySelector('#customParent');
+    doc.body.removeChild(parent);
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called if the document has no browsing context');
+}, 'Test detached callback if removing perent of custom element. ' +
+    'Document has no browsing context');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+
+    doc.registerElement('x-f', {prototype: proto});
+    doc.body.innerHTML = '<div><x-f id="x-f"></x-f></div>';
+    doc.body.innerHTML = '';
+
+    assert_equals(proto.detachedCallbackCalledCounter, 0,
+        'Callback detached should not be called if the document has no browsing context');
+}, 'Test detached callback if removing perent of custom element via innerHTML property. ' +
+    'Document has no browsing context');
+
+
+var loseBrowsingContextTest = async_test('Test detached callback is not called ' +
+    'if document lose browsing context and custom element is removed');
+
+loseBrowsingContextTest.step(function() {
+    var iframe = newIFrame('../../resources/x-element.html');
+    iframe.onload = loseBrowsingContextTest.step_func(function(){
+        var doc = iframe.contentDocument;
+        var proto = newHTMLElementPrototype();
+        doc.registerElement('x-element', {prototype: proto});
+
+        var customElement = doc.querySelector('#x-element');
+        iframe.remove();
+        customElement.remove();
+
+        assert_equals(proto.detachedCallbackCalledCounter, 0,
+            'Callback detached should not be called if the document has no browsing context');
+        loseBrowsingContextTest.done();
+    });
+});
+
+
+var navigateTest = async_test('Test detached callback is not called, ' +
+    'if document\'s window is navigated to another document and custom element is removed');
+
+navigateTest.step(function() {
+    var iframe = newIFrame('../../resources/x-element.html');
+    iframe.onload = navigateTest.step_func(function() {
+        var doc = iframe.contentDocument;
+        var proto = newHTMLElementPrototype();
+        doc.registerElement('x-element', {prototype: proto});
+        customElement = doc.querySelector('#x-element');
+
+        iframe.onload = navigateTest.step_func(function() {
+            customElement.remove();
+            assert_equals(proto.detachedCallbackCalledCounter, 0,
+                'Callback detached should not be called ' +
+                'if the document has no browsing context');
+            navigateTest.done();
+            iframe.remove();
+        });
+        iframe.src = '../../resources/blank.html';
+    });
+});
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-with-browsing-context-test.html b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-with-browsing-context-test.html
new file mode 100644
index 000000000..31b06a907
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/custom-element-lifecycle/types-of-callbacks/detached-callback-with-browsing-context-test.html
@@ -0,0 +1,85 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Detached callback of a custom element should be called if document has browsing context</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="detached callback ... must be enqueued whenever custom element is removed from the document and this document has a browsing context.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    var customElement = doc.querySelector('#x-element');
+    doc.body.removeChild(customElement);
+    assert_equals(proto.detachedCallbackCalledCounter, 1, 'Callback detached should be ' +
+        'called if custom element is removed from the document with browsing context');
+}, 'Test detached callback is called if custom element is removed by method removeChild() ' +
+    'from document with browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    doc.body.innerHTML = '<div id="x-a-parent"><x-a id="x-a"></x-a></div>';
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-a', {prototype: proto});
+    var div = doc.querySelector('#x-a-parent');
+    doc.body.removeChild(div);
+    assert_equals(proto.detachedCallbackCalledCounter, 1, 'Callback detached should be ' +
+        'called if custom element is removed from the document with browsing context');
+}, 'Test detached callback is called if ancestor node of custom element ' +
+    'is removed by method removeChild() from document with browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    var customElement = doc.querySelector('#x-element');
+    var div = doc.createElement('div');
+    doc.body.replaceChild(div, customElement);
+    assert_equals(proto.detachedCallbackCalledCounter, 1, 'Callback detached should be ' +
+        'called if custom element is removed from the document with browsing context');
+}, 'Test detached callback is called if custom element is removed by method replaceChild() ' +
+    'from document with browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-b', {prototype: proto});
+    doc.body.innerHTML = '<div id="x-b-parent"><x-b id="x-b"></x-b></div>';
+    var parent = doc.querySelector('#x-b-parent');
+    var replacement = doc.createElement('div');
+    doc.body.replaceChild(replacement, parent);
+    assert_equals(proto.detachedCallbackCalledCounter, 1, 'Callback detached should be ' +
+        'called if custom element is removed from the document with browsing context');
+}, 'Test detached callback is called if ancestor node of custom element ' +
+    'is removed by method replaceChild() from document with browsing context');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-element', {prototype: proto});
+    doc.body.innerHTML = '';
+    assert_equals(proto.detachedCallbackCalledCounter, 1, 'Callback detached should be ' +
+        'called if custom element is removed from the document with browsing context');
+}, 'Test detached callback is called after changing custom element direct parent ' +
+    'innerHTML property in the document with browsing context');
+
+
+testInIFrame('../../resources/blank.html', function(doc) {
+    doc.body.innerHTML = '<div><x-c></x-c></div>';
+    var proto = newHTMLElementPrototype();
+    doc.registerElement('x-c', {prototype: proto});
+    doc.body.innerHTML = '';
+    assert_equals(proto.detachedCallbackCalledCounter, 1, 'Callback detached should be ' +
+        'called if custom element is removed from the document with browsing context');
+}, 'Test detached callback is called after changing custom element ancestor ' +
+    'innerHTML property in the document with browsing context');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/changing-is-attribute.html b/testing/web-platform/tests/custom-elements/v0/instantiating/changing-is-attribute.html
new file mode 100644
index 000000000..fb4338840
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/changing-is-attribute.html
@@ -0,0 +1,158 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Changing IS attribute of the custom element must not affect this element's custom element type, after element is instantiated</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="After a custom element is instantiated, changing the value of the IS attribute must not affect this element's custom element type">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    var customElement = new GeneratedConstructor();
+    doc.registerElement('x-b');
+    customElement.setAttribute('is', 'x-b');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-a');
+}, 'Test custom element type, after assigning IS attribute value. ' +
+    'Element is created by constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-c');
+    doc.registerElement('x-d');
+    doc.body.innerHTML = '<x-c id="x-c"></x-c>';
+    var customElement = doc.querySelector('#x-c');
+    customElement.setAttribute('is', 'x-d');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-c');
+}, 'Test custom element type, after assigning IS attribute value. ' +
+    'Element is created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-e id="x-e"></x-e>';
+    var customElement = doc.querySelector('#x-e');
+    customElement.setAttribute('is', 'x-f');
+    var GeneratedConstructor = doc.registerElement('x-e');
+    doc.registerElement('x-f');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-e');
+}, 'Test custom element type, after assigning IS attribute value to unresolved element. ' +
+    'Element is created via innerHTML property');
+
+
+testInIFrame('../resources/x-element.html', function(doc) {
+    var GeneratedConstructor = doc.registerElement('x-element');
+    doc.registerElement('y-element');
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('is', 'y-element');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-element');
+}, 'Test custom element type, after assigning IS attribute value. ' +
+    'Element is defined in loaded HTML document');
+
+
+testInIFrame('../resources/x-element.html', function(doc) {
+    var customElement = doc.querySelector('#x-element');
+    customElement.setAttribute('is', 'y-element');
+    var GeneratedConstructor = doc.registerElement('x-element');
+    doc.registerElement('y-element');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-element');
+}, 'Test custom element type, after assigning IS attribute value to unresolved element. ' +
+    'Element is defined in loaded HTML document');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) !== -1) {
+            return;
+        }
+        var name = 'y-' + tagName;
+        var obj = doc.createElement(tagName);
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+        if (HTML5_TABLE_ELEMENTS.indexOf(tagName) !== -1) {
+            doc.body.innerHTML =
+                '<table>' +
+                '<' + tagName + ' id="custom-element" is="' + name + '"></' + tagName + '>' +
+                '</table>';
+        } else {
+            doc.body.innerHTML =
+                '<' + tagName + ' id="custom-element" is="' + name + '"></' + tagName + '>';
+        }
+        var customElement = doc.querySelector('#custom-element');
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be '+ name);
+
+        var name2 = 'y-a-' + tagName;
+        doc.registerElement(name2);
+        customElement.setAttribute('is', name2);
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be ' + name);
+    });
+}, 'Test custom element type after changing IS attribute value. ' +
+    'Element is HTML5 element with IS attribute referring to custom element type');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var localName = 'z-a';
+    var obj = doc.createElement('a');
+    var proto = Object.create(obj.constructor.prototype);
+    var GeneratedConstructor = doc.registerElement(localName, {prototype: proto, extends: 'a'});
+    doc.body.innerHTML = '<a id="custom-element" is="' + localName + '"></a>';
+    var customElement = doc.querySelector('#custom-element');
+
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var name = 'z-a-' + tagName;
+        var htmlElement = doc.createElement(tagName);
+        var htmlElementProto = Object.create(htmlElement.constructor.prototype);
+        doc.registerElement(name, {prototype: htmlElementProto, extends: tagName});
+        customElement.setAttribute('is', name);
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be ' + localName);
+    });
+}, 'Test custom element type after changing IS attribute value several times. ' +
+    'Element is HTML5 element with IS attribute referring to custom element type');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-g');
+    doc.registerElement('x-h');
+    doc.body.innerHTML = '<x-g id="x-g" is="x-h"></x-g>';
+    var customElement = doc.querySelector('#x-g');
+    customElement.removeAttribute('is');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-g');
+}, 'Test custom element type, after removing IS attribute value. ' +
+    'Element is created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var obj = doc.createElement('a');
+    var proto = Object.create(obj.constructor.prototype);
+    var GeneratedConstructor = doc.registerElement('x-i', {prototype: proto, extends: 'a'});
+    doc.body.innerHTML = '<a id="x-i" is="x-i"></a>';
+    var customElement = doc.querySelector('#x-i');
+    customElement.removeAttribute('is');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be x-i');
+}, 'Test custom element type, after removing IS attribute value. ' +
+    'Element is HTML5 element with IS attribute referring to custom element type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-is-attribute.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-is-attribute.html
new file mode 100644
index 000000000..0e18bf651
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-is-attribute.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element constructor sets value of IS attribute to custom element type, if it is not equal to name</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If TYPE is not the same as NAME, set the value of ELEMENT's IS attribute to TYPE">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) !== -1) {
+            return;
+        }
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.getAttribute('is'), name,
+            'Value of the IS attribute should be set to type');
+    });
+}, 'Test that the constructor of a type extension sets the IS attribute value to the type');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) !== -1) {
+            return;
+        }
+        var name = 'x-b-' + tagName;
+        var GeneratedConstructor = doc.registerElement(name);
+        var customElement = new GeneratedConstructor();
+
+        assert_false(customElement.hasAttribute('is'),
+            'IS attribute should not present if local name is the same as type');
+    });
+}, 'Test that the constructor of a custom element does not set the IS attribute if local name is the same as type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-local-name.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-local-name.html
new file mode 100644
index 000000000..28f6ca33f
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-local-name.html
@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element constructor sets local name to the name from custom element definition</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="Set ELEMENT's local name to NAME">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    var customElement = new GeneratedConstructor();
+    assert_equals(customElement.localName, 'x-a',
+        'Custom element local name should be equal to the name in custom element definition');
+}, 'Custom element constructor sets local name to the name from custom element definition');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.localName, tagName,
+            'Custom element local name should be equal to the name in custom element definition');
+    });
+}, 'Custom element constructor sets local name to the name from custom element definition. ' +
+    'Test constructor of extended HTML element');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-namespace.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-namespace.html
new file mode 100644
index 000000000..7278086ac
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-namespace.html
@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element constructor sets local namespace to the namespace from custom element definition</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Custom element constructor sets custom element namespace to the namespace in custom element definition">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    var customElement = new GeneratedConstructor();
+    assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+        'Custom element namespace should be equal to namespace in custom element definition');
+}, 'Custom element constructor sets namespace to the namespace from custom element definition');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+            'Custom element namespace should be equal to namespace in custom element definition');
+    });
+}, 'Custom element constructor sets namespace to the namespace from custom element definition. ' +
+    'Test constructor of extended HTML element');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-node-document.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-node-document.html
new file mode 100644
index 000000000..3112b36da
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-node-document.html
@@ -0,0 +1,100 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element constructor sets owner document to the document, where custom element type is registered</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Custom element constructor sets custom element node document to the document, where custom element type is registered">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    var customElement = new GeneratedConstructor();
+    assert_equals(customElement.ownerDocument, doc,
+        'Custom element owner document should be the document, where custom element ' +
+        'type is registered');
+}, 'Custom element constructor sets owner document to the document, where custom element ' +
+    'type is registered');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.ownerDocument, doc,
+            'Custom element owner document should be the document, where custom element ' +
+            'type is registered');
+    });
+}, 'Custom element constructor sets owner document to the document, where custom element ' +
+    'type is registered. Test constructor of extended HTML element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var sharedRegistryDocument = doc.implementation.createHTMLDocument('Document 2');
+
+    var name = 'x-c';
+    var GeneratedConstructor = doc.registerElement(name);
+    var customElement = new GeneratedConstructor();
+    assert_equals(customElement.ownerDocument, doc,
+        'Custom element owner document should be the document, where custom element ' +
+        'type is registered');
+
+    var name2 = 'x-d';
+    var GeneratedConstructor2 = sharedRegistryDocument.registerElement(name2);
+    var customElement2 = new GeneratedConstructor2();
+    assert_equals(customElement2.ownerDocument, sharedRegistryDocument,
+        'Custom element owner document should be the document, where custom element ' +
+        'type is registered');
+}, 'Custom element constructor sets owner document to the document, where custom element ' +
+    'type is registered. Test different documents with shared registry');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var sharedRegistryDocument = doc.implementation.createHTMLDocument('Document 2');
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-e-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName
+        });
+        var customElement = new GeneratedConstructor();
+        assert_equals(customElement.ownerDocument, doc,
+            'Custom element owner document should be the document, where custom element ' +
+            'type is registered');
+
+        var obj2 = sharedRegistryDocument.createElement(tagName);
+        var name2 = 'x-f-' + tagName;
+        var proto2 = Object.create(obj2.constructor.prototype);
+        var GeneratedConstructor2 = sharedRegistryDocument.registerElement(name2, {
+            prototype: proto2,
+            extends: tagName
+        });
+        var customElement2 = new GeneratedConstructor2();
+        assert_equals(customElement2.ownerDocument, sharedRegistryDocument,
+            'Custom element owner document should be the document, where custom element ' +
+            'type is registered');
+    });
+}, 'Custom element constructor sets owner document to the document, where custom element ' +
+    'type is registered. Test constructor of extended HTML element for different documents ' +
+    'with shared registry');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-prototype.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-prototype.html
new file mode 100644
index 000000000..0158af511
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-constructor-prototype.html
@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element constructor prototype is the prototype object specified in element definition</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Custom element constructor prototype is the prototype object specified in element definition">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(SVGElement.prototype);
+    var GeneratedConstructor = doc.registerElement('x-a', {
+        prototype: proto,
+        extends: 'p'
+    });
+    assert_true(GeneratedConstructor.prototype === proto,
+        'Custom element constructor must have the prototype specified in registerElement()');
+}, 'If custom element type is registered with prototype, the custom element ' +
+   'constructor should have the prototype specified in registerElement() call');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-prototype.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-prototype.html
new file mode 100644
index 000000000..2b298ea74
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-prototype.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element prototype is the prototype object specified in element definition</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Custom element prototype is the prototype object specified in element definition">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(SVGElement.prototype);
+    var GeneratedConstructor = doc.registerElement('x-a', {
+        prototype: proto,
+        extends: 'p'
+    });
+    var customElement = new GeneratedConstructor();
+
+    assert_true(Object.getPrototypeOf(customElement) === proto,
+        'Custom element instance must have the prototype specified in registerElement()');
+}, 'If custom element type is registered with prototype, the custom element ' +
+    'instance should have the prototype specified in registerElement() call');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-is-attribute.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-is-attribute.html
new file mode 100644
index 000000000..c18290d0e
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-is-attribute.html
@@ -0,0 +1,73 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Instantiation of custom element: custom element type is given as the value of the IS attribute</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The custom element type is given to a custom element at the time of its instantation in one of the two ways: ... 2. As the value of the IS attribute of the custom element.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) !== -1) {
+            return;
+        }
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+
+        if (HTML5_TABLE_ELEMENTS.indexOf(tagName) !== -1) {
+            doc.body.innerHTML =
+                '<table>' +
+                '<' + tagName + ' id="custom-element" is="' + name + '"></' + tagName + '>' +
+                '</table>';
+        } else {
+            doc.body.innerHTML =
+                '<' + tagName + ' id="custom-element" is="' + name + '"></' + tagName + '>';
+        }
+        var customElement = doc.querySelector('#custom-element');
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be the type, specified as value of IS attribute');
+    });
+}, 'Instantiation of custom element: custom element type is given as the value of ' +
+    'the IS attribute');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) !== -1) {
+            return;
+        }
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        if (HTML5_TABLE_ELEMENTS.indexOf(tagName) !== -1) {
+            doc.body.innerHTML =
+                '<table>' +
+                '<' + tagName + ' id="custom-element" is="' + name + '"></' + tagName + '>' +
+                '</table>';
+        } else {
+            doc.body.innerHTML =
+                '<' + tagName + ' id="custom-element" is="' + name + '"></' + tagName + '>';
+        }
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+
+        var customElement = doc.querySelector('#custom-element');
+
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be the type, specified as value of IS attribute');
+    });
+}, 'Instantiation of custom element: custom element type is given as the value ' +
+    'of the IS attribute. Custom element is unresolved at first');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name-and-is-attribute.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name-and-is-attribute.html
new file mode 100644
index 000000000..c55e2cc25
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name-and-is-attribute.html
@@ -0,0 +1,101 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Instantiation of custom element: the custom tag must win over the type extension</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="If both types of custom element types are provided at the time of element's instantiation, the custom tag must win over the type extension">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    doc.registerElement('x-b');
+    doc.body.innerHTML = '<x-a id="x-a" is="x-b"></x-a>';
+    var customElement = doc.querySelector('#x-a');
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the type, specified in the local name of the element');
+}, 'Custom element type must be taken from the local name of the element even ' +
+    'if IS attribute provided.');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.registerElement('x-d');
+    doc.body.innerHTML = '<x-c id="x-c" is="x-d"></x-c>';
+    var customElement = doc.querySelector('#x-c');
+
+    var GeneratedConstructor = doc.registerElement('x-c');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the type, specified in the local name of the element');
+}, 'Custom element type must be taken from the local name of the element even ' +
+    'if IS attribute provided. Custom element is unresolved at first');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-f');
+    doc.body.innerHTML = '<x-f id="x-f" is="x-e"></x-f>';
+    var customElement = doc.querySelector('#x-f');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the type, specified in local name of the element');
+
+    doc.registerElement('x-e');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the type, specified in local name of the element');
+}, 'Custom element type must be taken from the local name of the element even if IS ' +
+    'attribute provided. There\'s no definition for the value of IS attribute at first');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-element');
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-d-' + tagName;
+        doc.registerElement(name, {
+            prototype: Object.create(obj.constructor.prototype),
+            extends: tagName
+        });
+        doc.body.innerHTML = '<x-element id="x-element" is="' + name + '"></x-element>';
+        var customElement = doc.querySelector('#x-element');
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be the local name of the custom element');
+    });
+}, 'Custom element type must be taken from the local name of the element even ' +
+    'if IS attribute provided. IS attribute refers to another custom element type, ' +
+    'which extends HTML5 elements');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.registerElement('y-element');
+
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-e-' + tagName;
+        var id = 'x-e-' + tagName;
+        doc.registerElement(name, {
+            prototype: Object.create(obj.constructor.prototype),
+            extends: tagName
+        });
+        doc.body.innerHTML = '<' + name + ' id="' + id + '" is="y-element"></' + name + '>';
+        var customElement = doc.querySelector('#' + id);
+        // We have <x-e-a is='y-element'>. Custom element type for this will be
+        // HTMLElement, not x-e-a (for x-e-a there should be <a is='x-e-a'>...)
+        assert_class_string(customElement, 'HTMLElement',
+            'Custom element type should be HTMLElement');
+    });
+}, 'Custom element type must be taken from the local name of the custom element even ' +
+    'if IS attribute provided. The element extends HTML5 elements, IS attribute refers ' +
+    'to another custom element type.');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name.html b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name.html
new file mode 100644
index 000000000..0f0d46f0a
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/custom-element-type-local-name.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Instantiation of custom element: custom element type is given via the local name of the custom element</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The custom element type is given to a custom element at the time of its instantation in one of the two ways: 1. As the local name of the custom element.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    doc.body.innerHTML = '<x-a id="x-a"></x-a>';
+    var customElement = doc.querySelector('#x-a');
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the type, specified by the local name of ' +
+        'the custom element');
+}, 'Test custom element type, which is given via the local name of the custom element. ' +
+    'Custom element created via innerHTML property');
+
+
+testInIFrame('../resources/x-element.html', function(doc) {
+    var GeneratedConstructor = doc.registerElement('x-element');
+    var xelement = doc.querySelector('#x-element');
+    assert_equals(Object.getPrototypeOf(xelement), GeneratedConstructor.prototype,
+        'Custom element type should be the type, specified by the local name of ' +
+        'the custom element');
+}, 'Test custom element type, which is given via the local name of the custom element. ' +
+    'Custom element is defined in loaded HTML document');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-local-name.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-local-name.html
new file mode 100644
index 000000000..f59d6dcb8
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-local-name.html
@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() and Document.createElementNS() create custom element of type, specified by localName argument</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If an element definition with matching localName, namespace, and TYPE is not registered with token's document, set TYPE to localName">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name1 = 'x-a';
+    var name2 = 'x-b';
+    var GeneratedConstructor = doc.registerElement(name1);
+    var customElement = doc.createElement(name1, name2);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the local name of the custom element');
+}, 'Test Document.createElement() creates custom element of type, ' +
+    'specified by localName argument, if an element definition with matching localName, ' +
+    'namespace, and type is not registered');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name1 = 'x-c';
+    var name2 = 'x-d';
+    var GeneratedConstructor = doc.registerElement(name1);
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name1, name2);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the local name of the custom element');
+}, 'Test Document.createElementNS() creates custom element of type, ' +
+    'specified by localName argument, if an element definition with matching ' +
+    'localName, namespace, and type is not registered');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-type-extension.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-type-extension.html
new file mode 100644
index 000000000..3df042676
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-interface-type-is-a-type-extension.html
@@ -0,0 +1,69 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() and Document.createElementNS() create custom element of type, specified by typeExtension argument</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If an element definition with matching localName, namespace, and TYPE is registered then typeExtension is a TYPE">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name1 = 'x-a';
+    var GeneratedConstructor1 = doc.registerElement(name1);
+    var name2 = 'x-b';
+    var GeneratedConstructor2 = doc.registerElement(name2);
+    var customElement = doc.createElement(name1, name2);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor2.prototype,
+        'Custom element type should be the type extension of the custom element');
+}, 'Test Document.createElement() creates custom element of type, ' +
+    'specified by typeExtension argument');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name1 = 'x-c';
+    var GeneratedConstructor1 = doc.registerElement(name1);
+    var name2 = 'x-d';
+    var GeneratedConstructor2 = doc.registerElement(name2);
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name1, name2);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor2.prototype,
+        'Custom element type should be the type extension of the custom element');
+}, 'Test Document.createElementNS() creates custom element of type, ' +
+    'specified by typeExtension argument');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name1 = 'x-e';
+    var name2 = 'x-f';
+    var GeneratedConstructor2 = doc.registerElement(name2);
+    var customElement = doc.createElement(name1, name2);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor2.prototype,
+        'Custom element type should be the type extension of the custom element');
+}, 'Test Document.createElement() creates custom element of type, ' +
+    'specified by typeExtension argument. Definition for localName is absent');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name1 = 'x-g';
+    var name2 = 'x-h';
+    var GeneratedConstructor2 = doc.registerElement(name2);
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name1, name2);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor2.prototype,
+        'Custom element type should be the type extension of the custom element');
+}, 'Test Document.createElementNS() creates custom element of type, ' +
+    'specified by typeExtension argument. Definition for localName is absent');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-is-attribute.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-is-attribute.html
new file mode 100644
index 000000000..374ec5922
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-is-attribute.html
@@ -0,0 +1,71 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() and Document.createElementNS() set IS attribute to type</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If TYPE is not the same as localName, set the value of ELEMENT's IS attribute to TYPE">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = doc.createElement(tagName, name);
+        assert_equals(customElement.getAttribute('is'), name,
+            'Value of the IS attribute should be set to type by Document.createElement()');
+    });
+}, 'Test Document.createElement() sets the element\'s IS attribute value to type, ' +
+    'if type is not the same as localName');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var name = 'x-b-' + tagName;
+        var customElement = doc.createElement(tagName, name);
+        assert_equals(customElement.getAttribute('is'), name,
+            'Value of the IS attribute should be set to type by Document.createElement()');
+    });
+}, 'Test Document.createElement() sets the element\'s IS attribute value to type, ' +
+    'if type is not the same as localName and an element definition with matching ' +
+    'localName, namespace, and type is not registered');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-c-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = doc.createElementNS(HTML_NAMESPACE, tagName, name);
+        assert_equals(customElement.getAttribute('is'), name,
+            'Value of the IS attribute should be set to type by Document.createElementNS()');
+    });
+}, 'Test Document.createElementNS() sets the element\'s IS attribute value to type, ' +
+    'if type is not the same as localName');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var name = 'x-d-' + tagName;
+        var customElement = doc.createElementNS(HTML_NAMESPACE, tagName, name);
+        assert_equals(customElement.getAttribute('is'), name,
+            'Value of the IS attribute should be set to type by Document.createElementNS()');
+    });
+}, 'Test Document.createElementNS() sets the element\'s IS attribute value to type, ' +
+    'if type is not the same as localNameand and an element definition with matching ' +
+    'localName, namespace, and type is not registered ');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-namespace.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-namespace.html
new file mode 100644
index 000000000..60d501219
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-namespace.html
@@ -0,0 +1,68 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() sets custom element namespace to HTML Namespace</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Namespace for createElement is HTML Namespace">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-a';
+    doc.registerElement(name);
+    var customElement = doc.createElement(name);
+    assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+        'Custom element namespace should be HTML Namespace');
+}, 'Test Document.createElement() sets custom element namespace to HTML Namespace');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-b';
+    var customElement = doc.createElement(name);
+    assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+        'Custom element namespace should be HTML Namespace');
+}, 'Test Document.createElement() sets custom element namespace to HTML Namespace ' +
+    'and an element definition with matching localName, namespace, and type is not registered');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-c-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        doc.registerElement(name, {
+            prototype: Object.create(proto),
+            extends: tagName
+        });
+        var customElement = doc.createElement(tagName, name);
+        assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+            'Custom element namespace for the element extending ' + tagName +
+            ' should be HTML Namespace');
+    });
+}, 'Document.createElement() sets custom element namespace to HTML Namespace. ' +
+    'Custom element is extending standard HTML tag');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var name = 'x-d-' + tagName;
+        var customElement = doc.createElement(tagName, name);
+        assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+            'Custom element namespace for the element with tag name ' + tagName +
+            ' and type name ' + name + ' should be HTML Namespace');
+    });
+}, 'Document.createElement() sets custom element namespace to HTML Namespace. ' +
+    'Document.createElement() is called with standard HTML tag name and ' +
+    'type without registered custom element of such type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-is-a-type.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-is-a-type.html
new file mode 100644
index 000000000..ce7c933e2
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-is-a-type.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() and Document.createElementNS() create custom element of type, specified by typeExtension argument</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Let TYPE be typeExtension, or localName if typeExtension is not present">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = doc.createElement(tagName, name);
+
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be ' + name);
+    });
+}, 'Test Document.createElement() creates custom element of type, ' +
+    'specified by typeExtension argument');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = doc.createElementNS(HTML_NAMESPACE, tagName, name);
+
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be ' + name);
+    });
+}, 'Test Document.createElementNS() creates custom element of type, ' +
+    'specified by typeExtension argument');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-unresolved.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-unresolved.html
new file mode 100644
index 000000000..3eaadf312
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-extension-unresolved.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() and Document.createElementNS() create custom element of type, specified by localName argument</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If an element definition with matching localName, namespace, and TYPE is not registered with token's document, set TYPE to localName">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test (function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var customElement = doc.createElement(tagName, name);
+        assert_equals(Object.getPrototypeOf(customElement), Object.getPrototypeOf(obj),
+            'Unregistered custom element type should be a local name');
+
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Registered custom element type should be the type extension');
+    });
+}, 'If typeExtension is unresolved when createElement called then local name is a type');
+
+
+test (function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var customElement = doc.createElementNS(HTML_NAMESPACE, tagName, name);
+        assert_equals(Object.getPrototypeOf(customElement), Object.getPrototypeOf(obj),
+            'Custom element type should be a local name');
+
+        var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: tagName});
+        assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+            'Custom element type should be the type extension');
+    });
+}, 'If typeExtension is unresolved when createElementNS called then local name is a type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-is-a-local-name.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-is-a-local-name.html
new file mode 100644
index 000000000..487b14b9d
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/create-element-type-is-a-local-name.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() and Document.createElementNS() create custom element of type, specified by single localName argument</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Let TYPE be typeExtension, or localName if typeExtension is not present">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-a';
+    var GeneratedConstructor = doc.registerElement(name);
+    var customElement = doc.createElement(name);
+
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the local name of the custom element');
+}, 'Test Document.createElement() creates custom element of type, ' +
+    'specified by single localName argument');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-b';
+    var GeneratedConstructor = doc.registerElement(name);
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name);
+    assert_equals(Object.getPrototypeOf(customElement), GeneratedConstructor.prototype,
+        'Custom element type should be the local name of the custom element');
+}, 'Test Document.createElementNS() creates custom element of type, ' +
+    'specified by localName argument. Argument typeExtension is not passed');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element-ns.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element-ns.html
new file mode 100644
index 000000000..7bf09601c
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element-ns.html
@@ -0,0 +1,72 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElementNS() must enqueue created callback for registered custom element type</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Document.createElementNS() must enqueue created callback for registered custom element type">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var name = 'x-a';
+
+    doc.registerElement(name, {prototype: proto});
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name);
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be enqueued by Document.createElementNS()');
+}, 'Test Document.createElementNS() without typeExtension argument enqueues created callback');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var name = 'x-b';
+
+    doc.registerElement(name, {prototype: proto});
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name, name);
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be enqueued by Document.createElementNS()');
+}, 'Test Document.createElementNS() with typeExtension argument enqueues created callback');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var name = 'x-c';
+    var customElement = doc.createElementNS(HTML_NAMESPACE, name);
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Document.createElementNS() should not enqueue created callback ' +
+        'for unresolved custom element');
+
+    doc.registerElement(name, {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after custom element is registered');
+}, 'Document.createElementNS() should not enqueue created callback ' +
+    'for unresolved custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-d-' + tagName;
+        var proto = newCustomElementPrototype(Object.create(obj.constructor.prototype));
+        doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = doc.createElementNS(HTML_NAMESPACE, tagName, name);
+
+        assert_equals(proto.createdCallbackCalledCounter, 1,
+            'Callback created should be enqueued by Document.createElementNS()');
+    });
+}, 'Test Document.createElementNS() enqueues created callback for custom elements ' +
+    'that are extensions of HTML5 elements');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element.html b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element.html
new file mode 100644
index 000000000..dc05e01e1
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/extensions-to-document-interface/created-callback-create-element.html
@@ -0,0 +1,72 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Document.createElement() must enqueue created callback for registered custom element type</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Document.createElement() must enqueue created callback for registered custom element type">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-instantiate">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#types-of-callbacks">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var name = 'x-a';
+
+    doc.registerElement(name, {prototype: proto});
+    var customElement = doc.createElement(name);
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be enqueued by Document.createElement()');
+}, 'Test Document.createElement() without typeExtension argument enqueues created callback');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var name = 'x-b';
+
+    doc.registerElement(name, {prototype: proto});
+    var customElement = doc.createElement(name, name);
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be enqueued by Document.createElement()');
+}, 'Test Document.createElement() with typeExtension argument enqueues created callback');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = newHTMLElementPrototype();
+    var name = 'x-c';
+    var customElement = doc.createElement(name);
+    assert_equals(proto.createdCallbackCalledCounter, 0,
+        'Document.createElement() should not enqueue created callback ' +
+        'for unresolved custom element');
+
+    doc.registerElement(name, {prototype: proto});
+    assert_equals(proto.createdCallbackCalledCounter, 1,
+        'Callback created should be called after custom element is registered');
+}, 'Document.createElement() should not enqueue created callback ' +
+    'for unresolved custom element');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-d-' + tagName;
+        var proto = newCustomElementPrototype(Object.create(obj.constructor.prototype));
+        doc.registerElement(name, {prototype: proto, extends: tagName});
+        var customElement = doc.createElement(tagName, name);
+
+        assert_equals(proto.createdCallbackCalledCounter, 1,
+            'Callback created should be enqueued by Document.createElement()');
+    });
+}, 'Test Document.createElement() enqueues created callback for custom elements ' +
+    'that are extensions of HTML5 elements');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/non-configurable-constructor-property.html b/testing/web-platform/tests/custom-elements/v0/instantiating/non-configurable-constructor-property.html
new file mode 100644
index 000000000..ddb1ff9de
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/non-configurable-constructor-property.html
@@ -0,0 +1,41 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If prototype has a non-configurable property named constructor, Document.registerElement() throws NotSupportedError</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If  PROTOTYPE has a non-configurable property named constructor, throw a NotSupportedError and stop">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(HTMLElement.prototype);
+    Object.defineProperty(proto, 'constructor', {configurable: false});
+    assert_throws('NotSupportedError', function() {
+        doc.registerElement('x-a', {prototype: proto});
+    }, 'Exception should be thrown in case of attempt to register element ' +
+        'with a non-configurable property named constructor');
+}, 'Test Document.registerElement() throws NotSupportedError ' +
+    'if prototype has a non-configurable property named constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(HTMLElement.prototype);
+    Object.defineProperty(proto, 'constructor', {configurable: true});
+    try {
+        doc.registerElement('x-b', {prototype: proto});
+    } catch (e) {
+        assert_unreached('Exception should not be thrown in case of attempt to register ' +
+            'element with a configurable property named constructor');
+    }
+}, 'Test Document.registerElement() accepts prototype with a configurable ' +
+    'property named constructor without throwing errors');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/prototype-is-interface-prototype-object.html b/testing/web-platform/tests/custom-elements/v0/instantiating/prototype-is-interface-prototype-object.html
new file mode 100644
index 000000000..ad7f454f5
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/prototype-is-interface-prototype-object.html
@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If prototype is already an interface prototype object, Document.registerElement() throws a NotSupportedError</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If PROTOTYPE is already an interface prototype object for any interface object, throw a NotSupportedError and stop">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        assert_throws('NotSupportedError', function() {
+            doc.registerElement(name, {prototype: obj.constructor.prototype});
+        }, 'Exception should be thrown in case of attempt to register element ' +
+            'if prototype is already an interface prototype object (' + name + ')');
+    });
+}, 'Test Document.registerElement() throws NotSupportedError ' +
+    'if prototype is already an interface prototype object');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(HTMLElement.prototype);
+    doc.registerElement('x-b', {
+        prototype: proto
+    });
+    assert_throws('NotSupportedError', function() {
+        doc.registerElement('x-b', {
+            prototype: proto
+        });
+    }, 'Exception should be thrown if registring custom element type with already used prototype');
+}, 'Test Document.registerElement() throws NotSupportedError ' +
+    'if prototype is already used for another custom element type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/instantiating/unchanged-attribute.html b/testing/web-platform/tests/custom-elements/v0/instantiating/unchanged-attribute.html
new file mode 100644
index 000000000..3baa174cb
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/instantiating/unchanged-attribute.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<title>Custom element's type is immutable.</title>
+<meta name="author" title="Bon-Yong Lee" href="mailto:bylee78@gmail.com">
+<meta name="assert" content="After a custom element is instantiated, changing the value of the is attribute must not affect this element's custom element type.">
+<link rel="help" href="http://w3c.github.io/webcomponents/spec/custom/#instantiating-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<script type="text/javascript">
+test(function() {
+  var CustomButton = document.registerElement('custom-button', {
+    prototype: Object.create(HTMLButtonElement.prototype),
+    extends: 'button'
+  });
+  var customButton = document.createElement('button', 'custom-button');
+
+  assert_true(customButton instanceof CustomButton,
+              'A custom element is of the custom element type after ' +
+              'instantiation');
+  customButton.setAttribute('is', 'dirty');
+  assert_equals('dirty', customButton.getAttribute('is'),
+                'An attribute must be changed by method "setAttribute"');
+
+  assert_true(customButton instanceof CustomButton,
+              'A custom element is of the original custom element type even ' +
+              'after changing the \'is\' attribute');
+}, 'After a custom element is instantiated, changing the value of the is attribute must not affect this element\'s custom element type.');
+</script>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-default-namespace.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-default-namespace.html
new file mode 100644
index 000000000..6a1f532c7
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-default-namespace.html
@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Default namespace is HTML namespace</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Default namespace is HTML namespace">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    var customElement = new GeneratedConstructor();
+
+    assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+        'Custom element namespace should be HTML namespace');
+}, 'Default namespace is HTML namespace');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-b-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.namespaceURI, HTML_NAMESPACE,
+            'Custom element namespace should be HTML namespace');
+    });
+}, 'Default namespace is HTML namespace. Test constructor of extended HTML element');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-duplicate-definition.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-duplicate-definition.html
new file mode 100644
index 000000000..b3f661c4f
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-duplicate-definition.html
@@ -0,0 +1,56 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Check duplicate definition</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If there already exists a definition with the same TYPE, set ERROR to DuplicateDefinition and stop">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-a';
+    doc.registerElement(name);
+    assert_throws('NotSupportedError', function() {
+        doc.registerElement(name);
+    }, 'Exception should be thrown if definition with the same type already exists');
+}, 'Check duplicate definition');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-b';
+    doc.registerElement(name);
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        assert_throws('NotSupportedError', function() {
+            doc.registerElement(name, {
+                extends: tagName
+            });
+        }, 'Exception should be thrown if definition with the same type already exists');
+    });
+}, 'Check duplicate definition. Specify constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-c';
+    doc.registerElement(name, {
+        prototype: Object.create(HTMLAnchorElement.prototype),
+        extends: 'a'
+    });
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        assert_throws('NotSupportedError', function() {
+            doc.registerElement(name, {
+                extends: tagName
+            });
+        }, 'Exception should be thrown if definition with the same type already exists');
+    });
+}, 'Check duplicate definition. Test different prototypes and extends');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-invalid-type.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-invalid-type.html
new file mode 100644
index 000000000..5f2c09b4b
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-invalid-type.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If TYPE is an invalid custom element type, throw SyntaxError</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="If TYPE is an invalid custom element type, set ERROR to InvalidType and stop.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    assert_throws('SyntaxError', function() { doc.registerElement('1xa2'); },
+                  'Registering invalid custom element type should throw SyntaxError');
+}, 'Registering invalid custom element type should throw SyntaxError');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-local-name-lowercased.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-local-name-lowercased.html
new file mode 100644
index 000000000..7725e2efa
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-local-name-lowercased.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element local name should be converted to lower case if document is an HTML document</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If DOCUMENT is an HTML document, convert NAME to lowercase">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName.toUpperCase()
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.localName, tagName, 'Local name should be lowercased');
+    });
+}, 'Custom element local name should be lowercased if document is an HTML document');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-name-is-null.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-name-is-null.html
new file mode 100644
index 000000000..2b76818d6
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-name-is-null.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If NAME is null then localName must be set to TYPE</title>
+<meta name="author" title="Vasiliy Degtyarev" href="mailto:vasya@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If NAME is null then localName must be set to TYPE">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-a';
+    var proto = Object.create(HTMLElement.prototype);
+    var GeneratedConstructor = doc.registerElement(name, {prototype: proto});
+    var customElement = new GeneratedConstructor();
+
+    assert_equals(customElement.localName, name, 'LocalName should be a type in case of ' +
+        'attempt to register a custom element and local name is not provided');
+}, 'If NAME is not specified then localName must be set to TYPE');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var name = 'x-b';
+    var proto = Object.create(HTMLElement.prototype);
+    var GeneratedConstructor = doc.registerElement(name, {prototype: proto, extends: null});
+    var customElement = new GeneratedConstructor();
+
+    assert_equals(customElement.localName, name, 'LocalName should be a type in case of ' +
+        'attempt to register a custom element and name is null');
+}, 'If NAME is null then localName must be set to TYPE');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-no-interface-for-name.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-no-interface-for-name.html
new file mode 100644
index 000000000..6d72d60df
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-no-interface-for-name.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If element interface for name doesn't exists then error must be thrown</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If NAME was provided and is not null and if element interface for the name and namespace does not exist or is an interface for a custom element, set ERROR to InvalidName and stop">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    doc.registerElement('x-a');
+    assert_throws('NotSupportedError', function() {
+        doc.registerElement('x-b', {extends: 'x-a'});
+    }, 'Exception should be thrown in case of attempt to register ' +
+        'a custom element which extends another custom element');
+}, 'Exception should be thrown in case of attempt to register ' +
+    'a custom element which extends another custom element');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace-name-is-null.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace-name-is-null.html
new file mode 100644
index 000000000..dd6b61059
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace-name-is-null.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If namespace is SVG namespace and name is null then error must be thrown</title>
+<meta name="author" title="Vasiliy Degtyarev" href="mailto:vasya@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If namespace is SVG namespace and name is null then error must be thrown">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(SVGElement.prototype);
+    assert_throws('NotSupportedError', function() {
+        doc.registerElement('x-svg-a', {prototype: proto});
+    }, 'Exception should be thrown in case of attempt to register ' +
+        'a custom element with SVG namespace and name is not specified');
+}, 'Error should be thrown if namespace is SVG and local name is not specified');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(SVGElement.prototype);
+    assert_throws('NotSupportedError', function() {
+        doc.registerElement('x-svg-b', {prototype: proto, extends: null});
+    }, 'Exception should be thrown in case of attempt to register ' +
+        'a custom element with SVG namespace and name is null');
+}, 'Error should be thrown if namespace is SVG and local name is null');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace.html
new file mode 100644
index 000000000..497de2919
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-svg-namespace.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>For SVG prototype namespace is SVG namespace</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If PROTOTYPE's interface inherits from SVGElement, set NAMESPACE to SVG Namespace">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var proto = Object.create(SVGElement.prototype);
+    var GeneratedConstructor = doc.registerElement('x-a', {prototype: proto, extends: 'a'});
+    var customElement = new GeneratedConstructor();
+
+    assert_equals(customElement.namespaceURI, SVG_NAMESPACE,
+        'Custom element namespace should be SVG namespace');
+}, 'For SVG prototype namespace is SVG namespace');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-type-name-lowercased.html b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-type-name-lowercased.html
new file mode 100644
index 000000000..38dce801c
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/definition-construction-algorithm-type-name-lowercased.html
@@ -0,0 +1,41 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element type should be converted to lower case</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Custom element type should be lowercased">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('X-A');
+    var customElement = new GeneratedConstructor();
+
+    assert_equals(customElement.localName, 'x-a', 'Custom element type should be lowercased');
+}, 'Custom element type should be lowercased. Test constructor');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var obj = doc.createElement(tagName);
+        var name = 'x-a-' + tagName;
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName.toUpperCase()
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.localName, tagName, 'Local name should be lowercased');
+    });
+}, 'Custom element type should be lowercased. Test constructor of extended HTML element');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/element-registration-algorithm-no-registry.html b/testing/web-platform/tests/custom-elements/v0/registering/element-registration-algorithm-no-registry.html
new file mode 100644
index 000000000..6e9c20be3
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/element-registration-algorithm-no-registry.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>If document has no registry NotSupportedError is thrown</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="If REGISTRY does not exist, set ERROR to NoRegistry and stop.">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#dfn-element-registration-algorithm">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = document.implementation.createDocument(null, 'test', null);
+    assert_throws('NotSupportedError', function(){
+                      doc.registerElement('x-a');
+                  }, 'Registering valid custom element in document ' +
+                      'without registry should throw NotSupportedError');
+
+}, 'Registering valid custom element without options in document ' +
+    'without registry should throw NotSupportedError');
+
+
+test(function() {
+    var doc = document.implementation.createDocument(null, 'test', null);
+    var proto = Object.create(HTMLElement.prototype);
+
+    assert_throws('NotSupportedError', function(){
+                      doc.registerElement('x-b', { prototype: proto, extends: 'a'});
+                  }, 'Registering valid custom element in document ' +
+                      'without registry should throw NotSupportedError');
+
+}, 'Registering valid custom element with options in document ' +
+    'without registry should throw NotSupportedError');
+</script>
+</body>
+</html>
\ No newline at end of file
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-name.html b/testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-name.html
new file mode 100644
index 000000000..e276e834a
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-name.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Custom element local name is the lowercased value of the EXTENDS property, supplied to Document.registerElement()</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="Custom element local name is the lowercased value of the EXTENDS property">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-register">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        var name = 'x-' + tagName;
+        var obj = doc.createElement(tagName);
+        var proto = Object.create(obj.constructor.prototype);
+        var GeneratedConstructor = doc.registerElement(name, {
+            prototype: proto,
+            extends: tagName
+        });
+        var customElement = new GeneratedConstructor();
+
+        assert_equals(customElement.localName, tagName.toLowerCase(),
+            'Custom element local name should be a lowercased value of the EXTENDS property, ' +
+            'supplied to Document.registerElement()');
+    });
+}, 'Custom element local name is the lowercased value of the EXTENDS property, ' +
+    'supplied to Document.registerElement()');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-prototype.html b/testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-prototype.html
new file mode 100644
index 000000000..de397aacd
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/extensions-to-document-interface/custom-element-prototype.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Test prototype object of a custom element</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="If PROTOTYPE is null, let PROTOTYPE be the result of invoking Object.create with HTMLElement's interface prototype object as only argument">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#extensions-to-document-interface-to-register">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var GeneratedConstructor = doc.registerElement('x-a');
+    var customElement = new GeneratedConstructor();
+
+    assert_class_string(customElement, 'HTMLElement',
+        'Custom element should be a HTMLElement, ' +
+        'if its type is registered without prototype');
+}, 'Custom element should have HTMLElement prototype, ' +
+    'if its type is registered without prototype');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag-ref.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag-ref.html
new file mode 100644
index 000000000..33c36463c
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag-ref.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass reference file</title>
+<link rel="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<style>
+    body {
+        background-color: white;
+    }
+</style>
+<body>
+    <p>Test passes if x-element background below is red</p>
+    <x-element style="background-color: red;">
+        x-element
+    </x-element>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag.html
new file mode 100644
index 000000000..290e5b15c
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-custom-tag.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass matching custom tag</title>
+<link rel="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="The :unresolved pseudoclass must match all custom elements whose created callback has not yet been invoked">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#unresolved-element-pseudoclass">
+<link rel="match" href="unresolved-element-pseudoclass-css-test-custom-tag-ref.html">
+<style>
+    :unresolved {
+        background-color: red;
+    }
+    body {
+        background-color: white;
+    }
+</style>
+<body>
+    <p>Test passes if x-element background below is red</p>
+    <x-element>
+        x-element
+    </x-element>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag-ref.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag-ref.html
new file mode 100644
index 000000000..d49f3d768
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag-ref.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass reference file</title>
+<link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<style>
+    body {
+        background-color: white;
+    }
+</style>
+<body>
+    <p>Test passes if x-element background below is yellow</p>
+    <x-element style="background-color: yellow;">
+        x-element
+    </x-element>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag.html
new file mode 100644
index 000000000..3cd7b41d6
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-custom-tag.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass matching custom tag</title>
+<link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The :unresolved pseudoclass must match all custom elements whose created callback has not yet been invoked">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#unresolved-element-pseudoclass">
+<link rel="match" href="unresolved-element-pseudoclass-css-test-registered-custom-tag-ref.html">
+<style>
+    :unresolved {
+        background-color: red;
+    }
+    x-element {
+        background-color: yellow;
+    }
+    body {
+        background-color: white;
+    }
+</style>
+<body onload="document.registerElement('x-element');">
+    <p>Test passes if x-element background below is yellow</p>
+    <x-element>
+        x-element
+    </x-element>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension-ref.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension-ref.html
new file mode 100644
index 000000000..90baf9554
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension-ref.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass reference file</title>
+<link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<style>
+    body {
+        background-color: white;
+    }
+</style>
+<body>
+    <p>Test passes if x-element background below is yellow</p>
+    <a is="x-element" style="background-color: yellow;">
+        x-element
+    </a>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension.html
new file mode 100644
index 000000000..65921bd41
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-registered-type-extension.html
@@ -0,0 +1,33 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass matching type extension</title>
+<link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The :unresolved pseudoclass must match all custom elements whose created callback has not yet been invoked">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#unresolved-element-pseudoclass">
+<link rel="match" href="unresolved-element-pseudoclass-css-test-registered-type-extension-ref.html">
+<style>
+    :unresolved {
+        background-color: red;
+    }
+    a {
+        background-color: yellow;
+    }
+    body {
+        background-color: white;
+    }
+</style>
+<script>
+function registerXElement() {
+    var obj = document.createElement('a');
+    var proto = Object.create(obj.constructor.prototype);
+    document.registerElement('x-element', { prototype: proto, extends: 'a'});
+}
+</script>
+<body onload="registerXElement();">
+    <p>Test passes if x-element background below is yellow</p>
+    <a is="x-element">
+        x-element
+    </a>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension-ref.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension-ref.html
new file mode 100644
index 000000000..9865f2e39
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension-ref.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass reference file</title>
+<link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<style>
+    body {
+        background-color: white;
+    }
+</style>
+<body>
+    <p>Test passes if x-element background below is red</p>
+    <a is="x-element" style="background-color: red;">
+        x-element
+    </a>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension.html
new file mode 100644
index 000000000..60f39125a
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-css-test-type-extension.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<html>
+<title>The :unresolved pseudoclass matching type extension</title>
+<link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The :unresolved pseudoclass must match all custom elements whose created callback has not yet been invoked">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#unresolved-element-pseudoclass">
+<link rel="match" href="unresolved-element-pseudoclass-css-test-type-extension-ref.html">
+<style>
+    :unresolved {
+        background-color: red;
+    }
+    body {
+        background-color: white;
+    }
+</style>
+<body>
+    <p>Test passes if x-element background below is red</p>
+    <a is="x-element">
+        x-element
+    </a>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector-all.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector-all.html
new file mode 100644
index 000000000..2ddc2afc2
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector-all.html
@@ -0,0 +1,190 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>The :unresolved pseudoclass matching with Document.querySelectorAll()</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="assert" content="The :unresolved pseudoclass must match all custom elements whose created callback has not yet been invoked">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#unresolved-element-pseudoclass">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-a></x-a>';
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 1,
+        'Unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-a',
+        'Document.querySelectorAll(\':unresolved\') should return x-a element');
+}, 'Test that single unresolved custom element is accessible ' +
+    'by Document.querySelectorAll(\':unresolved\')');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-b></x-b>';
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 1,
+        'Unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-b',
+        'Document.querySelectorAll(\':unresolved\') should return x-b element');
+
+    doc.registerElement('x-b');
+    queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 0,
+        'Registered custom element should not be accessible by :unresolved pseudoclass');
+}, 'Test that single registered custom element is not accessible by :unresolved');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-c></x-c><x-d></x-d>';
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 2,
+        'All unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-c',
+        'First custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-c');
+    assert_equals(queryResult.item(1).localName, 'x-d',
+        'Second custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-d');
+
+    doc.registerElement('x-c');
+    queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 1,
+        'Only unresolved custom elements should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-d',
+        'Custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-d');
+}, 'If there are more than one unresolved custom element then all of them accessible ' +
+    'by Document.querySelectorAll(\':unresolved\')');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var customElement = doc.createElement('x-e');
+    doc.body.appendChild(customElement);
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 1,
+        'Unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-e',
+        'Custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-e');
+}, 'Unresolved custom element, created via Document.createElement(), should be ' +
+    'accessible by Document.querySelectorAll(\':unresolved\')');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-f><x-g></x-g></x-f>';
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 2,
+        'All unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-f',
+        'First custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-f');
+    assert_equals(queryResult.item(1).localName, 'x-g',
+        'Second custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-g');
+
+    doc.registerElement('x-g');
+    queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 1,
+        'Only unresolved custom elements should be accessible by :unresolved pseudoclass');
+    assert_equals(queryResult.item(0).localName, 'x-f',
+        'Custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-f');
+}, 'All unresolved custom element including nested ones are accessible ' +
+    'by Document.querySelectorAll(\':unresolved\')');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 1,
+        'Unresolved custom element should be accessible by ' +
+        'Document.querySelectorAll(\':unresolved\')');
+    assert_equals(queryResult.item(0).localName, 'x-element',
+        'Custom element returned by Document.querySelectorAll(\':unresolved\') ' +
+        'should be x-element');
+}, 'Unresolved custom element should be accessible by ' +
+    'Document.querySelectorAll(\':unresolved\') in a loaded document');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) === -1) {
+            var obj = doc.createElement(tagName);
+            var name = 'x-h-' + tagName;
+            var id = 'x-h-' + tagName + '-id';
+            if (HTML5_TABLE_ELEMENTS.indexOf(tagName) !== -1) {
+                doc.body.innerHTML =
+                    '<table>' +
+                    '<' + tagName + ' id="' + id + '" is="' + name + '"></' + tagName + '>' +
+                    '</table>';
+            } else {
+                doc.body.innerHTML =
+                    '<' + tagName + ' id="' + id + '" is="' + name + '"></' + tagName + '>';
+            }
+            var queryResult = doc.querySelectorAll(':unresolved');
+
+            assert_not_equals(queryResult, null,
+                'Unresolved custom element should be accessible by :unresolved pseudoclass');
+            assert_equals(queryResult.item(0).id, id,
+                'ID of element returned by Document.querySelectorAll(\':unresolved\') ' +
+                'should be ' + id);
+
+            var proto = Object.create(obj.constructor.prototype);
+            doc.registerElement(name, {prototype: proto, extends: tagName});
+            var queryResult2 = doc.querySelectorAll(':unresolved');
+
+            assert_equals(queryResult2.length, 0,
+                'Registered custom element should not be accessible by :unresolved pseudoclass');
+        }
+    });
+}, 'Test that Document.querySelectorAll(\':unresolved\') returns unresolved custom elements, ' +
+    'extending HTML elements by IS attribute');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-i><a is="x-j"></a></x-i><x-k></x-k><b is="x-l"/>';
+    var queryResult = doc.querySelectorAll(':unresolved');
+
+    assert_equals(queryResult.length, 4,
+        'All unresolved custom element should be accessible by :unresolved pseudoclass');
+
+    var elementNames = [
+        queryResult.item(0).localName,
+        queryResult.item(1).localName,
+        queryResult.item(2).localName,
+        queryResult.item(3).localName];
+    assert_array_equals(elementNames, ['x-i', 'a', 'x-k', 'b'],
+        'Document.querySelectorAll(\':unresolved\') return unexpected result');
+
+    var isAttributes = [
+        queryResult.item(0).getAttribute('is'),
+        queryResult.item(1).getAttribute('is'),
+        queryResult.item(2).getAttribute('is'),
+        queryResult.item(3).getAttribute('is')];
+    assert_array_equals(isAttributes, [null, 'x-j', null, 'x-l'],
+        'Document.querySelectorAll(\':unresolved\') return unexpected result');
+}, 'Test Document.querySelectorAll(\':unresolved\') returns mix of custom elements of different types');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector.html
new file mode 100644
index 000000000..47b7e5c47
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-element-pseudoclass/unresolved-element-pseudoclass-matching-query-selector.html
@@ -0,0 +1,161 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>The :unresolved pseudoclass matching with Document.querySelector()</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="The :unresolved pseudoclass must match all custom elements whose created callback has not yet been invoked">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#unresolved-element-pseudoclass">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-a></x-a>';
+    var customElement = doc.querySelector(':unresolved');
+
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved');
+    assert_equals(customElement.localName, 'x-a',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-a');
+}, 'Test that unresolved custom element is accessible by Document.querySelector(\':unresolved\')');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-b></x-b>';
+    var customElement = doc.querySelector(':unresolved');
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved');
+    assert_equals(customElement.localName, 'x-b',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-b');
+
+    doc.registerElement('x-b');
+    customElement = doc.querySelector(':unresolved');
+    assert_equals(customElement, null,
+        'Registered custom element should not be accessible by :unresolved pseudoclass');
+}, 'Test that registered custom element are not accessible by :unresolved');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-c></x-c><x-d></x-d>';
+    var customElement = doc.querySelector(':unresolved');
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(customElement.localName, 'x-c',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-c');
+
+    doc.registerElement('x-c');
+    customElement = doc.querySelector(':unresolved');
+    assert_not_equals(customElement, null,
+        'Unresolved custom elements should be accessible by :unresolved pseudoclass');
+    assert_equals(customElement.localName, 'x-d',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-d');
+}, 'If there are more than one unresolved custom element, all of them should be ' +
+    'accessible by :unresolved pseudoclass');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var customElement = doc.createElement('x-e');
+    doc.body.appendChild(customElement);
+    var queryResult = doc.querySelector(':unresolved');
+
+    assert_not_equals(queryResult, null,
+        'Unresolved custom element should be accessible by :unresolved');
+    assert_equals(queryResult.localName, 'x-e',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-e');
+}, 'Unresolved custom element, created via Document.createElement(), should be ' +
+    'accessible by Document.querySelector(\':unresolved\')');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<div><x-f></x-f><div>';
+    var customElement = doc.querySelector(':unresolved');
+
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved');
+    assert_equals(customElement.localName, 'x-f',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-f');
+}, 'Unresolved custom element inside div element should be accessible by ' +
+    ':unresolved pseudoclass');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-h><x-g></x-g></x-h>';
+    var customElement = doc.querySelector(':unresolved');
+
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved pseudoclass');
+    assert_equals(customElement.localName, 'x-h',
+        'Custom element returned by Document.querySelector(\':unresolved\') ' +
+        'should be x-h');
+
+    doc.registerElement('x-h');
+    customElement = doc.querySelector(':unresolved');
+
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved pseudoclass');
+	assert_equals(customElement.localName, 'x-g',
+        'Custom element returned by Document.querySelector(\':unresolved\') ' +
+        'should be x-g');
+}, 'All unresolved custom element including nested ones should be accessible ' +
+    'by Document.querySelector(\':unresolved\')');
+
+
+testInIFrame('../../resources/x-element.html', function(doc) {
+    var customElement = doc.querySelector(':unresolved');
+
+    assert_not_equals(customElement, null,
+        'Unresolved custom element should be accessible by :unresolved');
+    assert_equals(customElement.localName, 'x-element',
+        'Custom element returned by Document.querySelector(\':unresolved\') should be x-element');
+}, 'Document.querySelector(): Unresolved custom element should be accessible by :unresolved ' +
+    'in loaded document');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+
+    HTML5_ELEMENTS.forEach(function(tagName) {
+        if (HTML5_DOCUMENT_ELEMENTS.indexOf(tagName) === -1) {
+            var obj = doc.createElement(tagName);
+            var name = 'x-i-' + tagName;
+            var id = 'x-i-' + tagName + '-id';
+            if (HTML5_TABLE_ELEMENTS.indexOf(tagName) !== -1) {
+                doc.body.innerHTML =
+                    '<table>' +
+                    '<' + tagName + ' id="' + id + '" is="' + name + '"></' + tagName + '>' +
+                    '</table>';
+            } else {
+                doc.body.innerHTML =
+                    '<' + tagName + ' id="' + id + '" is="' + name + '"></' + tagName + '>';
+            }
+            var customElement = doc.querySelector(':unresolved');
+
+            assert_not_equals(customElement, null,
+                'Unresolved custom element should be accessible by :unresolved pseudoclass');
+            assert_equals(customElement.id, id,
+                'ID of element returned by Document.querySelector(\':unresolved\') ' +
+                'should be ' + id);
+
+            var proto = Object.create(obj.constructor.prototype);
+            doc.registerElement(name, {prototype: proto, extends: tagName});
+            var customElement2 = doc.querySelector(':unresolved');
+
+            assert_equals(customElement2, null,
+                'Registered custom element should not be accessible by :unresolved pseudoclass');
+        }
+    });
+}, 'Test that Document.querySelector(\':unresolved\') returns custom element, ' +
+    'extending HTML elements by IS attribute');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-element.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-element.html
new file mode 100644
index 000000000..492c75b72
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-element.html
@@ -0,0 +1,56 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Unresolved element interface must be HTMLElement, if the namespace is HTML Namespace</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="When an unresolved element is created, it's element interface must be HTMLElement, if the namespace is HTML Namespace">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML = '<x-a id="x-a"></x-a>';
+    var customElement = doc.querySelector('#x-a');
+
+    assert_not_equals(customElement, null, 'Unregistered custom element should not be null');
+
+    assert_class_string(customElement, 'HTMLElement',
+        'Unresolved custom element must be a HTML element');
+}, 'Test interface of unresolved element, created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var customElement = doc.createElement('x-b');
+
+    assert_class_string(customElement, 'HTMLElement',
+        'Unresolved custom element must be a HTML element');
+}, 'Test interface of unresolved element, created by Document.createElement');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var customElement = doc.createElementNS(HTML_NAMESPACE, 'x-c');
+
+    assert_class_string(customElement, 'HTMLElement',
+        'Unresolved custom element must be a HTML element');
+}, 'Test interface of unresolved element, created by Document.createElementNS');
+
+
+testInIFrame('../resources/x-element.html', function(doc) {
+    var customElement = doc.getElementById('x-element');
+
+    assert_not_equals(customElement, null, 'Unregistered custom element should not be null');
+
+    assert_class_string(customElement, 'HTMLElement',
+        'Unresolved custom element must be a HTML element');
+}, 'Test unresolved element interface in loaded HTML document');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-unknown-element.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-unknown-element.html
new file mode 100644
index 000000000..70c23d3c9
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-html-unknown-element.html
@@ -0,0 +1,53 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Unresolved element interface must be HTMLUnknownElement, if the namespace is neither HTML Namespace nor SVG Namespace</title>
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="When an unresolved element is created, it's element interface must be HTMLUnknownElement, if the namespace is neither HTML Namespace nor SVG Namespace">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+var MATHML_NAMESPACE = 'http://www.w3.org/1998/Math/MathML';
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML =
+        '<math xmlns="' + MATHML_NAMESPACE + '">' +
+            '<x-a id="x-a"></x-a>' +
+        '</math>';
+    var xa = doc.querySelector('#x-a');
+
+    assert_not_equals(xa, null, 'Unregistered custom element should not be null');
+
+    // According https://code.google.com/p/chromium/issues/detail?id=336377
+    // expected class string is Element
+    assert_class_string(xa, 'Element', 'Unresolved custom element must be an Element');
+}, 'Test interface of unresolved element with MathML namespace, created via innerHTML property');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    var xa = doc.createElementNS(MATHML_NAMESPACE, 'x-b');
+
+    assert_class_string(xa, 'Element',
+        'Unresolved custom element must be a HTMLUnknownElement');
+}, 'Test interface of unresolved element with MathML namespace, ' +
+    'created by Document.createElementNS');
+
+
+testInIFrame('../resources/x-mathml-element.html', function(doc) {
+    var customElement = doc.getElementById('x-math-element');
+
+    assert_not_equals(customElement, null, 'Unregistered custom element should not be null');
+
+    assert_class_string(customElement, 'Element',
+        'Unresolved custom element must be a Element');
+}, 'Test interface of unresolved element in loaded HTML document with embedded MathML elements');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-svg-element.html b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-svg-element.html
new file mode 100644
index 000000000..4164b62dc
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/registering/unresolved-elements-interface-svg-element.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Unresolved element interface must be SVGElement, if the namespace is SVG Namespace</title>
+<meta name="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+<meta name="author" title="Vasiliy Degtyarev" href="mailto:vasya@unipro.ru">
+<meta name="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+<meta name="assert" content="When an unresolved element is created, it's element interface must be SVGElement if the namespace is SVG Namespace">
+<link rel="help" href="http://www.w3.org/TR/custom-elements/#registering-custom-elements">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+test(function() {
+    var doc = newHTMLDocument();
+    var xsvg = doc.createElementNS(SVG_NAMESPACE, 'x-svg');
+
+    assert_class_string(xsvg, 'SVGElement', 'Unresolved custom element must be a SVG element');
+}, 'Test interface of unresolved element with valid name, created by Document.createElementNS()');
+
+
+test(function() {
+    var doc = newHTMLDocument();
+    doc.body.innerHTML =
+        '<svg xmlns=' + SVG_NAMESPACE + ' version="1.1">' +
+            '<x-svg-a id="x-svg"></x-svg-a>' +
+        '</svg>';
+    var xsvg = doc.querySelector('#x-svg');
+
+    assert_class_string(xsvg, 'SVGElement', 'Unresolved custom element must be a SVG element');
+}, 'Test interface of unresolved element with valid name, created via innerHTML property');
+
+
+testInIFrame('../resources/x-svg-element.html', function(doc) {
+    var xsvg = doc.getElementById('x-svg-element');
+
+    assert_not_equals(xsvg, null, 'Unresolved custom element should not be null');
+
+    assert_class_string(xsvg, 'SVGElement',
+        'Unresolved custom element must be a SVG element');
+}, 'Test interface of unresolved element in loaded HTML document with embedded SVG elements');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/blank.html b/testing/web-platform/tests/custom-elements/v0/resources/blank.html
new file mode 100644
index 000000000..2e5697ba1
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/blank.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>Blank document</title>
+    <link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+</head>
+<body>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/import-master-async.html b/testing/web-platform/tests/custom-elements/v0/resources/import-master-async.html
new file mode 100644
index 000000000..0ecaafb29
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/import-master-async.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Import Master Document (asynchronous)</title>
+        <link rel="import" href="import.html" async>
+    </head>
+    <body>
+        <p>Master document body</p>
+    </body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/import-master.html b/testing/web-platform/tests/custom-elements/v0/resources/import-master.html
new file mode 100644
index 000000000..d91bcb9cd
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/import-master.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Import Master Document</title>
+        <link rel="import" href="import.html">
+    </head>
+    <body>
+        <p>Master document body</p>
+    </body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/import.html b/testing/web-platform/tests/custom-elements/v0/resources/import.html
new file mode 100644
index 000000000..dddc46701
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/import.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Import Document</title>
+    </head>
+    <body>
+        <p>Import Document body</p>
+    </body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/register-and-create-custom-element.html b/testing/web-platform/tests/custom-elements/v0/resources/register-and-create-custom-element.html
new file mode 100644
index 000000000..3aabff244
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/register-and-create-custom-element.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>Register and create custom element</title>
+    <link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+    <link rel="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+</head>
+<body>
+    <div id="log"></div>
+    <script>
+        var proto = Object.create(HTMLElement.prototype);
+        proto.createdCallback = function() {
+            document.querySelector('#log').textContent = 'Created callback was called';
+        };
+        document.registerElement('x-element', {prototype: proto});
+    </script>
+    <x-element id="x-element"></x-element>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/x-element.html b/testing/web-platform/tests/custom-elements/v0/resources/x-element.html
new file mode 100644
index 000000000..0c0d2daad
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/x-element.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>x-element custom element</title>
+    <link rel="author" title="Sergey G. Grekhov" href="mailto:sgrekhov@unipro.ru">
+</head>
+<body>
+    <x-element id="x-element"></x-element>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/x-mathml-element.html b/testing/web-platform/tests/custom-elements/v0/resources/x-mathml-element.html
new file mode 100644
index 000000000..3efdc2d00
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/x-mathml-element.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>Custom element in MathML namespace</title>
+    <link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+</head>
+<body>
+    <math xmlns="http://www.w3.org/1998/Math/MathML">
+        <x-math-element id="x-math-element"></x-math-element>
+    </math>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/resources/x-svg-element.html b/testing/web-platform/tests/custom-elements/v0/resources/x-svg-element.html
new file mode 100644
index 000000000..6cea85758
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/resources/x-svg-element.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>SVG custom element</title>
+    <link rel="author" title="Aleksei Yu. Semenov" href="mailto:a.semenov@unipro.ru">
+</head>
+<body>
+    <svg height="100" width="100">
+        <x-svg-element id="x-svg-element"></x-element>
+    </svg>
+</body>
+</html>
diff --git a/testing/web-platform/tests/custom-elements/v0/testcommon.js b/testing/web-platform/tests/custom-elements/v0/testcommon.js
new file mode 100644
index 000000000..5cddbe8bc
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/v0/testcommon.js
@@ -0,0 +1,286 @@
+/*
+Distributed under both the W3C Test Suite License [1] and the W3C
+3-clause BSD License [2]. To contribute to a W3C Test Suite, see the
+policies and contribution forms [3].
+
+[1] http://www.w3.org/Consortium/Legal/2008/04-testsuite-license
+[2] http://www.w3.org/Consortium/Legal/2008/03-bsd-license
+[3] http://www.w3.org/2004/10/27-testcases
+ */
+
+"use strict";
+
+var HTML5_ELEMENTS = [ 'a', 'abbr', 'address', 'area', 'article', 'aside',
+        'audio', 'b', 'base', 'bdi', 'bdo', 'blockquote', 'body', 'br',
+        'button', 'canvas', 'caption', 'cite', 'code', 'col', 'colgroup',
+        'command', 'datalist', 'dd', 'del', 'details', 'dfn', 'dialog', 'div',
+        'dl', 'dt', 'em', 'embed', 'fieldset', 'figcaption', 'figure',
+        'footer', 'form', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'head', 'header',
+        'hgroup', 'hr', 'html', 'i', 'iframe', 'img', 'input', 'ins', 'kbd',
+        'keygen', 'label', 'legend', 'li', 'link', 'map', 'mark', 'menu',
+        'meta', 'meter', 'nav', 'noscript', 'object', 'ol', 'optgroup',
+        'option', 'output', 'p', 'param', 'pre', 'progress', 'q', 'rp', 'rt',
+        'ruby', 's', 'samp', 'script', 'section', 'select', 'small', 'source',
+        'span', 'strong', 'style', 'sub', 'table', 'tbody', 'td', 'textarea',
+        'tfoot', 'th', 'thead', 'time', 'title', 'tr', 'track', 'u', 'ul',
+        'var', 'video', 'wbr' ];
+
+var HTML5_DOCUMENT_ELEMENTS = [ 'html', 'head', 'body' ];
+
+var HTML5_TABLE_ELEMENTS = [ 'caption', 'col', 'colgroup', 'tbody', 'td',
+        'tfoot', 'th', 'thead', 'tr' ];
+
+var EXTENDER_CHARS = [ 0x00B7, 0x02D0, 0x02D1, 0x0387, 0x0640, 0x0E46, 0x0EC6,
+        0x3005, 0x3031, 0x3032, 0x3033, 0x3034, 0x3035, 0x309D, 0x309E, 0x30FC,
+        0x30FD, 0x30FE ];
+
+var COMBINING_CHARS = [ 0x0300, 0x0301, 0x0302, 0x0303, 0x0304, 0x0305, 0x0306,
+        0x0307, 0x0308, 0x0309, 0x030A, 0x030B, 0x030C, 0x030D, 0x030E, 0x030F,
+        0x0310, 0x0311, 0x0312, 0x0313, 0x0314, 0x0315, 0x0316, 0x0317, 0x0318,
+        0x0319, 0x031A, 0x031B, 0x031C, 0x031D, 0x031E, 0x031F, 0x0320, 0x0321,
+        0x0322, 0x0323, 0x0324, 0x0325, 0x0326, 0x0327, 0x0328, 0x0329, 0x032A,
+        0x032B, 0x032C, 0x032D, 0x032E, 0x032F, 0x0330, 0x0331, 0x0332, 0x0333,
+        0x0334, 0x0335, 0x0336, 0x0337, 0x0338, 0x0339, 0x033A, 0x033B, 0x033C,
+        0x033D, 0x033E, 0x033F, 0x0340, 0x0341, 0x0342, 0x0343, 0x0344, 0x0345,
+        0x0360, 0x0361, 0x0483, 0x0484, 0x0485, 0x0486, 0x0591, 0x0592, 0x0593,
+        0x0594, 0x0595, 0x0596, 0x0597, 0x0598, 0x0599, 0x05A0, 0x05A1, 0x05A3,
+        0x05A4, 0x05A5, 0x05A6, 0x05A7, 0x05A8, 0x05A9, 0x05AA, 0x05AB, 0x05AC,
+        0x05AD, 0x05AE, 0x05AF, 0x05B0, 0x05B1, 0x05B2, 0x05B3, 0x05B4, 0x05B5,
+        0x05B6, 0x05B7, 0x05B8, 0x05B9, 0x05BB, 0x05BC, 0x05BD, 0x05BF, 0x05C1,
+        0x05C2, 0x05C4, 0x064B, 0x064C, 0x064D, 0x064E, 0x064F, 0x0650, 0x0651,
+        0x0652, 0x0670, 0x06D6, 0x06D7, 0x06D8, 0x06D9, 0x06DA, 0x06DB, 0x06DC,
+        0x06DD, 0x06DE, 0x06DF, 0x06E0, 0x06E1, 0x06E2, 0x06E3, 0x06E4, 0x06E7,
+        0x06E8, 0x06EA, 0x06EB, 0x06EC, 0x06ED, 0x0901, 0x0902, 0x0903, 0x093C,
+        0x093E, 0x093F, 0x0940, 0x0941, 0x0942, 0x0943, 0x0944, 0x0945, 0x0946,
+        0x0947, 0x0948, 0x0949, 0x094A, 0x094B, 0x094C, 0x094D, 0x0951, 0x0952,
+        0x0953, 0x0954, 0x0962, 0x0963, 0x0981, 0x0982, 0x0983, 0x09BC, 0x09BE,
+        0x09BF, 0x09C0, 0x09C1, 0x09C2, 0x09C3, 0x09C4, 0x09C7, 0x09C8, 0x09CB,
+        0x09CC, 0x09CD, 0x09D7, 0x09E2, 0x09E3, 0x0A02, 0x0A3C, 0x0A3E, 0x0A3F,
+        0x0A40, 0x0A41, 0x0A42, 0x0A47, 0x0A48, 0x0A4B, 0x0A4C, 0x0A4D, 0x0A70,
+        0x0A71, 0x0A81, 0x0A82, 0x0A83, 0x0ABC, 0x0ABE, 0x0ABF, 0x0AC0, 0x0AC1,
+        0x0AC2, 0x0AC3, 0x0AC4, 0x0AC5, 0x0AC7, 0x0AC8, 0x0AC9, 0x0ACB, 0x0ACC,
+        0x0ACD, 0x0B01, 0x0B02, 0x0B03, 0x0B3C, 0x0B3E, 0x0B3F, 0x0B40, 0x0B41,
+        0x0B42, 0x0B43, 0x0B47, 0x0B48, 0x0B4B, 0x0B4C, 0x0B4D, 0x0B56, 0x0B57,
+        0x0B82, 0x0B83, 0x0BBE, 0x0BBF, 0x0BC0, 0x0BC1, 0x0BC2, 0x0BC6, 0x0BC7,
+        0x0BC8, 0x0BCA, 0x0BCB, 0x0BCC, 0x0BCD, 0x0BD7, 0x0C01, 0x0C02, 0x0C03,
+        0x0C3E, 0x0C3F, 0x0C40, 0x0C41, 0x0C42, 0x0C43, 0x0C44, 0x0C46, 0x0C47,
+        0x0C48, 0x0C4A, 0x0C4B, 0x0C4C, 0x0C4D, 0x0C55, 0x0C56, 0x0C82, 0x0C83,
+        0x0CBE, 0x0CBF, 0x0CC0, 0x0CC1, 0x0CC2, 0x0CC3, 0x0CC4, 0x0CC6, 0x0CC7,
+        0x0CC8, 0x0CCA, 0x0CCB, 0x0CCC, 0x0CCD, 0x0CD5, 0x0CD6, 0x0D02, 0x0D03,
+        0x0D3E, 0x0D3F, 0x0D40, 0x0D41, 0x0D42, 0x0D43, 0x0D46, 0x0D47, 0x0D48,
+        0x0D4A, 0x0D4B, 0x0D4C, 0x0D4D, 0x0D57, 0x0E31, 0x0E34, 0x0E35, 0x0E36,
+        0x0E37, 0x0E38, 0x0E39, 0x0E3A, 0x0E47, 0x0E48, 0x0E49, 0x0E4A, 0x0E4B,
+        0x0E4C, 0x0E4D, 0x0E4E, 0x0EB1, 0x0EB4, 0x0EB5, 0x0EB6, 0x0EB7, 0x0EB8,
+        0x0EB9, 0x0EBB, 0x0EBC, 0x0EC8, 0x0EC9, 0x0ECA, 0x0ECB, 0x0ECC, 0x0ECD,
+        0x0F18, 0x0F19, 0x0F35, 0x0F37, 0x0F39, 0x0F3E, 0x0F3F, 0x0F71, 0x0F72,
+        0x0F73, 0x0F74, 0x0F75, 0x0F76, 0x0F77, 0x0F78, 0x0F79, 0x0F7A, 0x0F7B,
+        0x0F7C, 0x0F7D, 0x0F7E, 0x0F7F, 0x0F80, 0x0F81, 0x0F82, 0x0F83, 0x0F84,
+        0x0F86, 0x0F87, 0x0F88, 0x0F89, 0x0F8A, 0x0F8B, 0x0F90, 0x0F91, 0x0F92,
+        0x0F93, 0x0F94, 0x0F95, 0x0F97, 0x0F99, 0x0F9A, 0x0F9B, 0x0F9C, 0x0F9D,
+        0x0F9E, 0x0F9F, 0x0FA0, 0x0FA1, 0x0FA2, 0x0FA3, 0x0FA4, 0x0FA5, 0x0FA6,
+        0x0FA7, 0x0FA8, 0x0FA9, 0x0FAA, 0x0FAB, 0x0FAC, 0x0FAD, 0x0FB1, 0x0FB2,
+        0x0FB3, 0x0FB4, 0x0FB5, 0x0FB6, 0x0FB7, 0x0FB9, 0x20D0, 0x20D1, 0x20D2,
+        0x20D3, 0x20D4, 0x20D5, 0x20D6, 0x20D7, 0x20D8, 0x20D9, 0x20DA, 0x20DB,
+        0x20DC, 0x20E1, 0x302A, 0x302B, 0x302C, 0x302D, 0x302E, 0x302F, 0x3099,
+        0x309A ];
+
+var BASE_CHARS_SINGLE = [ 0x0386, 0x038C, 0x03DA, 0x03DC, 0x03DE, 0x03E0,
+        0x0559, 0x06D5, 0x093D, 0x09B2, 0x0A5E, 0x0A8D, 0x0ABD, 0x0AE0, 0x0B3D,
+        0x0B9C, 0x0CDE, 0x0E30, 0x0E84, 0x0E8A, 0x0E8D, 0x0EA5, 0x0EA7, 0x0EB0,
+        0x0EBD, 0x1100, 0x1109, 0x113C, 0x113E, 0x1140, 0x114C, 0x114E, 0x1150,
+        0x1159, 0x1163, 0x1165, 0x1167, 0x1169, 0x1175, 0x119E, 0x11A8, 0x11AB,
+        0x11BA, 0x11EB, 0x11F0, 0x11F9, 0x1F59, 0x1F5B, 0x1F5D, 0x1FBE, 0x2126,
+        0x212E ];
+
+var BASE_CHARS_RANGES = [ 0x0041, 0x005A, 0x0061, 0x007A, 0x00C0, 0x00D6,
+        0x00D8, 0x00F6, 0x00F8, 0x00FF, 0x0100, 0x0131, 0x0134, 0x013E, 0x0141,
+        0x0148, 0x014A, 0x017E, 0x0180, 0x01C3, 0x01CD, 0x01F0, 0x01F4, 0x01F5,
+        0x01FA, 0x0217, 0x0250, 0x02A8, 0x02BB, 0x02C1, 0x0388, 0x038A, 0x038E,
+        0x03A1, 0x03A3, 0x03CE, 0x03D0, 0x03D6, 0x03E2, 0x03F3, 0x0401, 0x040C,
+        0x040E, 0x044F, 0x0451, 0x045C, 0x045E, 0x0481, 0x0490, 0x04C4, 0x04C7,
+        0x04C8, 0x04CB, 0x04CC, 0x04D0, 0x04EB, 0x04EE, 0x04F5, 0x04F8, 0x04F9,
+        0x0531, 0x0556, 0x0561, 0x0586, 0x05D0, 0x05EA, 0x05F0, 0x05F2, 0x0621,
+        0x063A, 0x0641, 0x064A, 0x0671, 0x06B7, 0x06BA, 0x06BE, 0x06C0, 0x06CE,
+        0x06D0, 0x06D3, 0x06E5, 0x06E6, 0x0905, 0x0939, 0x0958, 0x0961, 0x0985,
+        0x098C, 0x098F, 0x0990, 0x0993, 0x09A8, 0x09AA, 0x09B0, 0x09B6, 0x09B9,
+        0x09DC, 0x09DD, 0x09DF, 0x09E1, 0x09F0, 0x09F1, 0x0A05, 0x0A0A, 0x0A0F,
+        0x0A10, 0x0A13, 0x0A28, 0x0A2A, 0x0A30, 0x0A32, 0x0A33, 0x0A35, 0x0A36,
+        0x0A38, 0x0A39, 0x0A59, 0x0A5C, 0x0A72, 0x0A74, 0x0A85, 0x0A8B, 0x0A8F,
+        0x0A91, 0x0A93, 0x0AA8, 0x0AAA, 0x0AB0, 0x0AB2, 0x0AB3, 0x0AB5, 0x0AB9,
+        0x0B05, 0x0B0C, 0x0B0F, 0x0B10, 0x0B13, 0x0B28, 0x0B2A, 0x0B30, 0x0B32,
+        0x0B33, 0x0B36, 0x0B39, 0x0B5C, 0x0B5D, 0x0B5F, 0x0B61, 0x0B85, 0x0B8A,
+        0x0B8E, 0x0B90, 0x0B92, 0x0B95, 0x0B99, 0x0B9A, 0x0B9E, 0x0B9F, 0x0BA3,
+        0x0BA4, 0x0BA8, 0x0BAA, 0x0BAE, 0x0BB5, 0x0BB7, 0x0BB9, 0x0C05, 0x0C0C,
+        0x0C0E, 0x0C10, 0x0C12, 0x0C28, 0x0C2A, 0x0C33, 0x0C35, 0x0C39, 0x0C60,
+        0x0C61, 0x0C85, 0x0C8C, 0x0C8E, 0x0C90, 0x0C92, 0x0CA8, 0x0CAA, 0x0CB3,
+        0x0CB5, 0x0CB9, 0x0CE0, 0x0CE1, 0x0D05, 0x0D0C, 0x0D0E, 0x0D10, 0x0D12,
+        0x0D28, 0x0D2A, 0x0D39, 0x0D60, 0x0D61, 0x0E01, 0x0E2E, 0x0E32, 0x0E33,
+        0x0E40, 0x0E45, 0x0E81, 0x0E82, 0x0E87, 0x0E88, 0x0E94, 0x0E97, 0x0E99,
+        0x0E9F, 0x0EA1, 0x0EA3, 0x0EAA, 0x0EAB, 0x0EAD, 0x0EAE, 0x0EB2, 0x0EB3,
+        0x0EC0, 0x0EC4, 0x0F40, 0x0F47, 0x0F49, 0x0F69, 0x10A0, 0x10C5, 0x10D0,
+        0x10F6, 0x1102, 0x1103, 0x1105, 0x1107, 0x110B, 0x110C, 0x110E, 0x1112,
+        0x1154, 0x1155, 0x115F, 0x1161, 0x116D, 0x116E, 0x1172, 0x1173, 0x11AE,
+        0x11AF, 0x11B7, 0x11B8, 0x11BC, 0x11C2, 0x1E00, 0x1E9B, 0x1EA0, 0x1EF9,
+        0x1F00, 0x1F15, 0x1F18, 0x1F1D, 0x1F20, 0x1F45, 0x1F48, 0x1F4D, 0x1F50,
+        0x1F57, 0x1F5F, 0x1F7D, 0x1F80, 0x1FB4, 0x1FB6, 0x1FBC, 0x1FC2, 0x1FC4,
+        0x1FC6, 0x1FCC, 0x1FD0, 0x1FD3, 0x1FD6, 0x1FDB, 0x1FE0, 0x1FEC, 0x1FF2,
+        0x1FF4, 0x1FF6, 0x1FFC, 0x212A, 0x212B, 0x2180, 0x2182, 0x3041, 0x3094,
+        0x30A1, 0x30FA, 0x3105, 0x312C, 0xAC00, 0xD7A3 ];
+
+var IDEOGRAPHIC_CHARS_SINGLE = [ 0x3007 ];
+
+var IDEOGRAPHIC_CHARS_RANGES = [ 0x3021, 0x3029, 0x4E00, 0x9FA5 ];
+
+var DIGIT_CHARS_RANGES = [ 0x0030, 0x0039, 0x0660, 0x0669, 0x06F0, 0x06F9,
+        0x0966, 0x096F, 0x09E6, 0x09EF, 0x0A66, 0x0A6F, 0x0AE6, 0x0AEF, 0x0B66,
+        0x0B6F, 0x0BE7, 0x0BEF, 0x0C66, 0x0C6F, 0x0CE6, 0x0CEF, 0x0D66, 0x0D6F,
+        0x0E50, 0x0E59, 0x0ED0, 0x0ED9, 0x0F20, 0x0F29 ];
+
+function CharsArray(array) {
+    this.array = array;
+}
+
+CharsArray.prototype.testEach = function(namingFunction, checkFunction) {
+    if (this.array != null) {
+        this.array.forEach(function(value) {
+            checkFunction(namingFunction(getCharCode(value)));
+        });
+    }
+};
+
+function CharRangesArray(array) {
+    this.array = array;
+}
+
+CharRangesArray.prototype.testEach = function(namingFunction, checkFunction) {
+    if (this.array != null) {
+        for (var i = 0; i < this.array.length; i += 2) {
+            var rangeStart = getCharCode(this.array[i]);
+            var rangeEnd = getCharCode(this.array[i+1]);
+            for (var c = rangeStart; c <= rangeEnd; c++) {
+                checkFunction(namingFunction(c));
+            }
+        }
+    }
+};
+
+function testCharCode(charCode, namingFunction, checkFunction) {
+    checkFunction(namingFunction(charCode));
+}
+
+var extenderChars = new CharsArray(EXTENDER_CHARS);
+var combiningChars = new CharsArray(COMBINING_CHARS);
+var baseCharsSingle = new CharsArray(BASE_CHARS_SINGLE);
+var baseCharsRanges = new CharRangesArray(BASE_CHARS_RANGES);
+var ideographicCharsSingle = new CharsArray(IDEOGRAPHIC_CHARS_SINGLE);
+var ideographicCharsRanges = new CharRangesArray(IDEOGRAPHIC_CHARS_RANGES);
+var digitCharsRanges = new CharRangesArray(DIGIT_CHARS_RANGES);
+
+// Helper function, which verifies that given custom element name is valid
+function checkValidName(name) {
+    var doc = newHTMLDocument();
+    try {
+        doc.registerElement(name);
+    } catch (e) {
+        assert_unreached('The custom element name \'' + name +
+            '\' should be registered without errors');
+    }
+}
+
+// Helper function, which verifies that given custom element name is invalid
+function checkInvalidName(name) {
+    var doc = newHTMLDocument();
+    assert_throws('SyntaxError', function() {
+            doc.registerElement(name);
+        }, 'Registering invalid custom element name \'' + name + '\' should fail');
+}
+
+// Helper function to extract character code from given object
+// expected input: either charater code or one character long string.
+function getCharCode(c) {
+    if (typeof(c) === 'string') {
+        assert_equals(1, c.length, 'Error in test: input string should be one character long');
+        c = c.charCodeAt(0);
+    }
+    assert_equals('number', typeof(c), 'Error in test: unexpected type for charater code');
+    return c;
+}
+
+var HTML_NAMESPACE = 'http://www.w3.org/1999/xhtml';
+var SVG_NAMESPACE = 'http://www.w3.org/2000/svg';
+
+function newHTMLDocument() {
+    return document.implementation.createHTMLDocument('Test Document');
+}
+
+// Creates new iframe and loads given url into it.
+// Returns reference to created iframe.
+function newIFrame(url) {
+    assert_not_equals(url, null, 'argument url should not be null');
+    var iframe = document.createElement('iframe');
+    iframe.src = url;
+    document.body.appendChild(iframe);
+    return iframe;
+}
+
+// Creates new iframe and loads given url into it.
+// Function f is bound to the iframe's onload event.
+// Function f receives iframe's contentDocument as argument.
+// The iframe is disposed after function f is executed.
+function testInIFrame(url, f, testName, testProps) {
+    var t = async_test(testName, testProps);
+    t.step(function() {
+        var iframe = newIFrame(url);
+        iframe.onload = t.step_func(function() {
+            try {
+                f(iframe.contentDocument);
+                t.done();
+            } finally {
+                iframe.remove();
+            }
+        });
+    });
+}
+
+// Helper function to create a prototype for custom element
+// with predefined callbacks
+function newHTMLElementPrototype() {
+    return newCustomElementPrototype(HTMLElement.prototype);
+}
+
+// Helper function to create a prototype for custom element
+// with predefined callbacks
+function newCustomElementPrototype(parent) {
+    var proto = Object.create(parent);
+    proto.createdCallbackThis = null;
+    proto.createdCallbackCalledCounter = 0;
+
+    proto.attachedCallbackThis = null;
+    proto.attachedCallbackCalledCounter = 0;
+
+    proto.detachedCallbackThis = null;
+    proto.detachedCallbackCalledCounter = 0;
+
+    proto.attributeChangedCallbackThis = null;
+    proto.attributeChangedCallbackCalledCounter = 0;
+    proto.attributeChangedCallbackArgs = null;
+
+    proto.createdCallback = function() {
+        proto.createdCallbackThis = this;
+        proto.createdCallbackCalledCounter++;
+    };
+    proto.attachedCallback = function() {
+        proto.attachedCallbackThis = this;
+        proto.attachedCallbackCalledCounter++;
+    };
+    proto.detachedCallback = function() {
+        proto.detachedCallbackThis = this;
+        proto.detachedCallbackCalledCounter++;
+    };
+    proto.attributeChangedCallback = function(arg1, arg2, arg3) {
+        proto.attributeChangedCallbackThis = this;
+        proto.attributeChangedCallbackCalledCounter++;
+        proto.attributeChangedCallbackArgs = [arg1, arg2, arg3];
+    };
+    return proto;
+}
-- 
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