diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_967000_button_tabView.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_967000_button_tabView.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* 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";
+
+add_task(function() {
+  info("Check Tab Groups button functionality");
+  let deferred = Promise.defer();
+  let timeout = null;
+
+  // add the Tab View button to the panel
+  CustomizableUI.addWidgetToArea("tabview-button", CustomizableUI.AREA_PANEL);
+
+  window.addEventListener("tabviewhidden", function tabViewHidden() {
+    clearTimeout(timeout);
+    window.removeEventListener("tabviewhidden", tabViewHidden, false);
+    ok(true, "Tab View is closed");
+    deferred.resolve();
+  }, false);
+
+  window.addEventListener("tabviewshown", function tabViewShown() {
+    window.removeEventListener("tabviewshown", tabViewShown, false);
+    ok(true, "Tab Groups are loaded");
+    // close tabs view
+    window.TabView.hide();
+    timeout = setTimeout(() => {
+      window.removeEventListener("tabviewhidden", tabViewHidden, false);
+      deferred.reject("Tabs view wasn't hidden within 20000ms");
+    }, 20000);
+  }, false);
+
+  // check the button's functionality
+  yield PanelUI.show();
+
+  let tabViewButton = document.getElementById("tabview-button");
+  ok(tabViewButton, "Tab Groups button was added to the Panel Menu");
+  tabViewButton.click();
+
+  yield deferred.promise;
+
+  ok(!isPanelUIOpen(), "The panel is closed");
+
+  if(isPanelUIOpen()) {
+    let panelHidePromise = promisePanelHidden(window);
+    PanelUI.hide();
+    yield panelHidePromise;
+  }
+});
+
+add_task(function asyncCleanup() {
+  // reset the panel to the default state
+  yield resetCustomization();
+  ok(CustomizableUI.inDefaultState, "UI is in default state again.");
+});