diff -r 000000000000 -r 6474c204b198 addon-sdk/source/test/test-window-observer.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/test/test-window-observer.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,61 @@
+/* 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 { Loader } = require("sdk/test/loader");
+const { open, close } = require("sdk/window/helpers");
+const { browserWindows: windows } = require("sdk/windows");
+const { isBrowser } = require('sdk/window/utils');
+const app = require("sdk/system/xul-app");
+
+exports["test unload window observer"] = function(assert, done) {
+  // Hacky way to be able to create unloadable modules via makeSandboxedLoader.
+  let loader = Loader(module);
+  let observer = loader.require("sdk/windows/observer").observer;
+  let opened = 0;
+  let closed = 0;
+  let windowsOpen = windows.length;
+
+  observer.on("open", onOpen);
+  observer.on("close", onClose);
+
+  // On Fennec, only test that the module does not throw an error
+  if (app.is("Fennec")) {
+    assert.pass("Windows observer did not throw on Fennec");
+    return cleanUp();
+  }
+
+  // Open window and close it to trigger observers.
+  open().
+    then(close).
+    then(loader.unload).
+    then(open).
+    then(close).
+    then(function() {
+      // Enqueuing asserts to make sure that assertion is not performed early.
+      assert.equal(1, opened, "observer open was called before unload only");
+      assert.equal(windowsOpen + 1, closed, "observer close was called before unload only");
+    }).
+    then(cleanUp, assert.fail);
+
+  function cleanUp () {
+    observer.removeListener("open", onOpen);
+    observer.removeListener("close", onClose);
+    done();
+  }
+
+  function onOpen(window) {
+    // Ignoring non-browser windows
+    if (isBrowser(window))
+      opened++;
+  }
+  function onClose(window) {
+    // Ignore non-browser windows & already opened `activeWindow` (unload will
+    // emit close on it even though it is not actually closed).
+    if (isBrowser(window))
+      closed++;
+  }
+};
+
+require("sdk/test").run(exports);