diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_967000_button_sync.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_967000_button_sync.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,46 @@
+/* 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/. */
+
+"use strict";
+
+let initialLocation = gBrowser.currentURI.spec;
+let newTab = null;
+
+add_task(function() {
+  info("Check Sync button functionality");
+  Services.prefs.setCharPref("identity.fxaccounts.remote.signup.uri", "http://example.com/");
+
+  // add the Sync button to the panel
+  CustomizableUI.addWidgetToArea("sync-button", CustomizableUI.AREA_PANEL);
+
+  // check the button's functionality
+  yield PanelUI.show();
+
+  let syncButton = document.getElementById("sync-button");
+  ok(syncButton, "The Sync button was added to the Panel Menu");
+  syncButton.click();
+
+  newTab = gBrowser.selectedTab;
+  yield promiseTabLoadEvent(newTab, "about:accounts");
+
+  is(gBrowser.currentURI.spec, "about:accounts", "Firefox Sync page opened");
+  ok(!isPanelUIOpen(), "The panel closed");
+
+  if(isPanelUIOpen()) {
+    let panelHidePromise = promisePanelHidden(window);
+    PanelUI.hide();
+    yield panelHidePromise;
+  }
+});
+
+add_task(function asyncCleanup() {
+  Services.prefs.clearUserPref("identity.fxaccounts.remote.signup.uri");
+  // reset the panel UI to the default state
+  yield resetCustomization();
+  ok(CustomizableUI.inDefaultState, "The panel UI is in default state again.");
+
+  // restore the tabs
+  gBrowser.addTab(initialLocation);
+  gBrowser.removeTab(newTab);
+});