diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_873501_handle_specials.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_873501_handle_specials.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,79 @@
+/* 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";
+
+const kToolbarName = "test-specials-toolbar";
+
+registerCleanupFunction(removeCustomToolbars);
+
+// Add a toolbar with two springs and the downloads button.
+add_task(function addToolbarWith2SpringsAndDownloadsButton() {
+  // Create the toolbar with a single spring:
+  createToolbarWithPlacements(kToolbarName, ["spring"]);
+  ok(document.getElementById(kToolbarName), "Toolbar should be created.");
+
+  // Check it's there with a generated ID:
+  assertAreaPlacements(kToolbarName, [/customizableui-special-spring\d+/]);
+  let [springId] = getAreaWidgetIds(kToolbarName);
+
+  // Add a second spring, check if that's there and doesn't share IDs
+  CustomizableUI.addWidgetToArea("spring", kToolbarName);
+  assertAreaPlacements(kToolbarName, [springId,
+                                      /customizableui-special-spring\d+/]);
+  let [, spring2Id] = getAreaWidgetIds(kToolbarName);
+
+  isnot(springId, spring2Id, "Springs shouldn't have identical IDs.");
+
+  // Try moving the downloads button to this new toolbar, between the two springs:
+  CustomizableUI.addWidgetToArea("downloads-button", kToolbarName, 1);
+  assertAreaPlacements(kToolbarName, [springId, "downloads-button", spring2Id]);
+  yield removeCustomToolbars();
+});
+
+// Add separators around the downloads button.
+add_task(function addSeparatorsAroundDownloadsButton() {
+  createToolbarWithPlacements(kToolbarName, ["separator"]);
+  ok(document.getElementById(kToolbarName), "Toolbar should be created.");
+
+  // Check it's there with a generated ID:
+  assertAreaPlacements(kToolbarName, [/customizableui-special-separator\d+/]);
+  let [separatorId] = getAreaWidgetIds(kToolbarName);
+
+  CustomizableUI.addWidgetToArea("separator", kToolbarName);
+  assertAreaPlacements(kToolbarName, [separatorId,
+                                      /customizableui-special-separator\d+/]);
+  let [, separator2Id] = getAreaWidgetIds(kToolbarName);
+
+  isnot(separatorId, separator2Id, "Separator ids shouldn't be equal.");
+
+  CustomizableUI.addWidgetToArea("downloads-button", kToolbarName, 1);
+  assertAreaPlacements(kToolbarName, [separatorId, "downloads-button", separator2Id]);
+  yield removeCustomToolbars();
+});
+
+// Add spacers around the downloads button.
+add_task(function addSpacersAroundDownloadsButton() {
+  createToolbarWithPlacements(kToolbarName, ["spacer"]);
+  ok(document.getElementById(kToolbarName), "Toolbar should be created.");
+
+  // Check it's there with a generated ID:
+  assertAreaPlacements(kToolbarName, [/customizableui-special-spacer\d+/]);
+  let [spacerId] = getAreaWidgetIds(kToolbarName);
+
+  CustomizableUI.addWidgetToArea("spacer", kToolbarName);
+  assertAreaPlacements(kToolbarName, [spacerId,
+                                      /customizableui-special-spacer\d+/]);
+  let [, spacer2Id] = getAreaWidgetIds(kToolbarName);
+
+  isnot(spacerId, spacer2Id, "Spacer ids shouldn't be equal.");
+
+  CustomizableUI.addWidgetToArea("downloads-button", kToolbarName, 1);
+  assertAreaPlacements(kToolbarName, [spacerId, "downloads-button", spacer2Id]);
+  yield removeCustomToolbars();
+});
+
+add_task(function asyncCleanup() {
+  yield resetCustomization();
+});