diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_987640_charEncoding.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_987640_charEncoding.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,62 @@
+/* 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 TEST_PAGE = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/test_967000_charEncoding_page.html";
+let newTab = null;
+
+add_task(function() {
+  info("Check Character Encoding panel functionality");
+
+  // add the Character Encoding button to the panel
+  CustomizableUI.addWidgetToArea("characterencoding-button",
+                                  CustomizableUI.AREA_PANEL);
+
+  newTab = gBrowser.addTab(TEST_PAGE);
+  yield promiseTabLoadEvent(gBrowser.selectedTab, TEST_PAGE);
+
+  yield PanelUI.show();
+  let charEncodingButton = document.getElementById("characterencoding-button");
+  charEncodingButton.click();
+
+  let characterEncodingView = document.getElementById("PanelUI-characterEncodingView");
+  let checkedButtons = characterEncodingView.querySelectorAll("toolbarbutton[checked='true']");
+  let initialEncoding = checkedButtons[0];
+  is(initialEncoding.getAttribute("label"), "Unicode", "The unicode encoding is initially selected");
+
+  // change the encoding
+  let encodings = characterEncodingView.querySelectorAll("toolbarbutton");
+  let newEncoding = encodings[0].hasAttribute("checked") ? encodings[1] : encodings[0];
+  let tabLoadPromise = promiseTabLoadEvent(gBrowser.selectedTab, TEST_PAGE);
+  newEncoding.click();
+  yield tabLoadPromise;
+
+  // check that the new encodng is applied
+  yield PanelUI.show();
+  charEncodingButton.click();
+  checkedButtons = characterEncodingView.querySelectorAll("toolbarbutton[checked='true']");
+  let selectedEncodingName = checkedButtons[0].getAttribute("label");
+  ok(selectedEncodingName != "Unicode", "The encoding was changed to " + selectedEncodingName);
+
+  // reset the initial encoding
+  yield PanelUI.show();
+  charEncodingButton.click();
+  tabLoadPromise = promiseTabLoadEvent(gBrowser.selectedTab, TEST_PAGE);
+  initialEncoding.click();
+  yield tabLoadPromise;
+  yield PanelUI.show();
+  charEncodingButton.click();
+  let checkedButtons = characterEncodingView.querySelectorAll("toolbarbutton[checked='true']");
+  is(checkedButtons[0].getAttribute("label"), "Unicode", "The encoding was reset to Unicode");
+});
+
+add_task(function asyncCleanup() {
+  // reset the panel to the default state
+  yield resetCustomization();
+  ok(CustomizableUI.inDefaultState, "The UI is in default state again.");
+
+  // remove the added tab
+  gBrowser.removeTab(newTab);
+});