1 files changed, 51 insertions, 0 deletions
diff --git a/devtools/client/styleeditor/test/browser_styleeditor_transition_rule.js b/devtools/client/styleeditor/test/browser_styleeditor_transition_rule.js
new file mode 100644
index 000000000..d52ec41fc
--- /dev/null
+++ b/devtools/client/styleeditor/test/browser_styleeditor_transition_rule.js
@@ -0,0 +1,51 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TESTCASE_URI = TEST_BASE_HTTPS + "simple.html";
+
+const NEW_RULE = "body { background-color: purple; }";
+
+add_task(function* () {
+  let { ui } = yield openStyleEditorForURL(TESTCASE_URI);
+
+  is(ui.editors.length, 2, "correct number of editors");
+
+  let editor = ui.editors[0];
+  yield openEditor(editor);
+
+  // Set text twice in a row
+  let styleChanges = listenForStyleChange(editor.styleSheet);
+
+  editor.sourceEditor.setText(NEW_RULE);
+  editor.sourceEditor.setText(NEW_RULE + " ");
+
+  yield styleChanges;
+
+  let rules = yield ContentTask.spawn(gBrowser.selectedBrowser, 0,
+  function* (index) {
+    let sheet = content.document.styleSheets[index];
+    return [...sheet.cssRules].map(rule => rule.cssText);
+  });
+
+  // Test that we removed the transition rule, but kept the rule we added
+  is(rules.length, 1, "only one rule in stylesheet");
+  is(rules[0], NEW_RULE, "stylesheet only contains rule we added");
+});
+
+/* Helpers */
+
+function openEditor(editor) {
+  let link = editor.summary.querySelector(".stylesheet-name");
+  link.click();
+
+  return editor.getSourceEditor();
+}
+
+function listenForStyleChange(sheet) {
+  let deferred = defer();
+  sheet.on("style-applied", deferred.resolve);
+  return deferred.promise;
+}