diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/update/tests/unit_aus_update/canCheckForAndCanApplyUpdates.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/update/tests/unit_aus_update/canCheckForAndCanApplyUpdates.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,134 @@
+/* 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/.
+ */
+
+function run_test() {
+  setupTestCommon();
+
+  // Verify write access to the custom app dir
+  logTestInfo("testing write access to the application directory");
+  let testFile = getCurrentProcessDir();
+  testFile.append("update_write_access_test");
+  testFile.create(AUS_Ci.nsIFile.NORMAL_FILE_TYPE, PERMS_FILE);
+  do_check_true(testFile.exists());
+  testFile.remove(false);
+  do_check_false(testFile.exists());
+
+  standardInit();
+
+  if (IS_WIN) {
+    // Create a mutex to prevent being able to check for or apply updates.
+    logTestInfo("attempting to create mutex");
+    let handle = createMutex(getPerInstallationMutexName());
+
+    logTestInfo("testing that the mutex was successfully created");
+    do_check_neq(handle, null);
+
+    // Check if available updates cannot be checked for when there is a mutex
+    // for this installation.
+    logTestInfo("testing nsIApplicationUpdateService:canCheckForUpdates is " +
+                "false when there is a mutex");
+    do_check_false(gAUS.canCheckForUpdates);
+
+    // Check if updates cannot be applied when there is a mutex for this
+    // installation.
+    logTestInfo("testing nsIApplicationUpdateService:canApplyUpdates is " +
+                "false when there is a mutex");
+    do_check_false(gAUS.canApplyUpdates);
+
+    logTestInfo("destroying mutex");
+    closeHandle(handle)
+  }
+
+  // Check if available updates can be checked for
+  logTestInfo("testing nsIApplicationUpdateService:canCheckForUpdates is true");
+  do_check_true(gAUS.canCheckForUpdates);
+  // Check if updates can be applied
+  logTestInfo("testing nsIApplicationUpdateService:canApplyUpdates is true");
+  do_check_true(gAUS.canApplyUpdates);
+
+  if (IS_WIN) {
+    // Attempt to create a mutex when application update has already created one
+    // with the same name.
+    logTestInfo("attempting to create mutex");
+    let handle = createMutex(getPerInstallationMutexName());
+
+    logTestInfo("testing that the mutex was not successfully created");
+    do_check_eq(handle, null);
+  }
+
+  doTestFinish();
+}
+
+if (IS_WIN) {
+  /**
+   * Determines a unique mutex name for the installation.
+   *
+   * @return Global mutex path.
+   */
+  function getPerInstallationMutexName() {
+    let hasher = AUS_Cc["@mozilla.org/security/hash;1"].
+                 createInstance(AUS_Ci.nsICryptoHash);
+    hasher.init(hasher.SHA1);
+
+    let exeFile = Services.dirsvc.get(XRE_EXECUTABLE_FILE, AUS_Ci.nsILocalFile);
+
+    let converter = AUS_Cc["@mozilla.org/intl/scriptableunicodeconverter"].
+                    createInstance(AUS_Ci.nsIScriptableUnicodeConverter);
+    converter.charset = "UTF-8";
+    let data = converter.convertToByteArray(exeFile.path.toLowerCase());
+
+    hasher.update(data, data.length);
+    return "Global\\MozillaUpdateMutex-" + hasher.finish(true);
+  }
+
+  /**
+   * Closes a Win32 handle.
+   *
+   * @param  aHandle
+   *         The handle to close.
+   */
+  function closeHandle(aHandle) {
+    let lib = ctypes.open("kernel32.dll");
+    let CloseHandle = lib.declare("CloseHandle",
+                                  ctypes.winapi_abi,
+                                  ctypes.int32_t, /* success */
+                                  ctypes.void_t.ptr); /* handle */
+    CloseHandle(aHandle);
+    lib.close();
+  }
+
+  /**
+   * Creates a mutex.
+   *
+   * @param  aName
+   *         The name for the mutex.
+   * @return The Win32 handle to the mutex.
+   */
+  function createMutex(aName) {
+    const INITIAL_OWN = 1;
+    const ERROR_ALREADY_EXISTS = 0xB7;
+    let lib = ctypes.open("kernel32.dll");
+    let CreateMutexW = lib.declare("CreateMutexW",
+                                   ctypes.winapi_abi,
+                                   ctypes.void_t.ptr, /* return handle */
+                                   ctypes.void_t.ptr, /* security attributes */
+                                   ctypes.int32_t, /* initial owner */
+                                   ctypes.jschar.ptr); /* name */
+
+    let handle = CreateMutexW(null, INITIAL_OWN, aName);
+    lib.close();
+    let alreadyExists = ctypes.winLastError == ERROR_ALREADY_EXISTS;
+    if (handle && !handle.isNull() && alreadyExists) {
+      closeHandle(handle);
+      handle = null;
+    }
+
+    if (handle && handle.isNull()) {
+      handle = null;
+    }
+
+    return handle;
+  }
+}