1 files changed, 64 insertions, 0 deletions
diff --git a/testing/modules/TestUtils.jsm b/testing/modules/TestUtils.jsm
new file mode 100644
index 000000000..901a73557
--- /dev/null
+++ b/testing/modules/TestUtils.jsm
@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This module implements a number of utilities useful for testing.
+ *
+ * Additions to this module should be generic and useful to testing multiple
+ * features. Utilities only useful to a sepcific testing framework should live
+ * in a module specific to that framework, such as BrowserTestUtils.jsm in the
+ * case of mochitest-browser-chrome.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "TestUtils",
+];
+
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+this.TestUtils = {
+  executeSoon(callbackFn) {
+    Services.tm.mainThread.dispatch(callbackFn, Ci.nsIThread.DISPATCH_NORMAL);
+  },
+
+  /**
+   * Waits for the specified topic to be observed.
+   *
+   * @param {string} topic
+   *        The topic to observe.
+   * @param {function} checkFn [optional]
+   *        Called with (subject, data) as arguments, should return true if the
+   *        notification is the expected one, or false if it should be ignored
+   *        and listening should continue. If not specified, the first
+   *        notification for the specified topic resolves the returned promise.
+   *
+   * @note Because this function is intended for testing, any error in checkFn
+   *       will cause the returned promise to be rejected instead of waiting for
+   *       the next notification, since this is probably a bug in the test.
+   *
+   * @return {Promise}
+   * @resolves The array [subject, data] from the observed notification.
+   */
+  topicObserved(topic, checkFn) {
+    return new Promise((resolve, reject) => {
+      Services.obs.addObserver(function observer(subject, topic, data) {
+        try {
+          if (checkFn && !checkFn(subject, data)) {
+            return;
+          }
+          Services.obs.removeObserver(observer, topic);
+          resolve([subject, data]);
+        } catch (ex) {
+          Services.obs.removeObserver(observer, topic);
+          reject(ex);
+        }
+      }, topic, false);
+    });
+  },
+};