diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_934113_menubar_removable.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_934113_menubar_removable.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+/* 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";
+
+// Attempting to drag the menubar to the navbar shouldn't work.
+add_task(function() {
+  yield startCustomizing();
+  let menuItems = document.getElementById("menubar-items");
+  let navbar = document.getElementById("nav-bar");
+  let menubar = document.getElementById("toolbar-menubar");
+  // Force the menu to be shown.
+  const kAutohide = menubar.getAttribute("autohide");
+  menubar.setAttribute("autohide", "false");
+  simulateItemDrag(menuItems, navbar.customizationTarget);
+
+  is(getAreaWidgetIds("nav-bar").indexOf("menubar-items"), -1, "Menu bar shouldn't be in the navbar.");
+  ok(!navbar.querySelector("#menubar-items"), "Shouldn't find menubar items in the navbar.");
+  ok(menubar.querySelector("#menubar-items"), "Should find menubar items in the menubar.");
+  isnot(getAreaWidgetIds("toolbar-menubar").indexOf("menubar-items"), -1,
+        "Menubar items shouldn't be missing from the navbar.");
+  menubar.setAttribute("autohide", kAutohide);
+  yield endCustomizing();
+});
+
+add_task(function asyncCleanup() {
+  yield endCustomizing();
+  yield resetCustomization();
+});