diff -r 000000000000 -r 6474c204b198 toolkit/components/osfile/tests/xpcshell/test_available_free_space.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/osfile/tests/xpcshell/test_available_free_space.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,38 @@
+/* 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";
+
+Components.utils.import("resource://gre/modules/osfile.jsm");
+Components.utils.import("resource://gre/modules/Services.jsm");
+
+do_register_cleanup(function() {
+  Services.prefs.setBoolPref("toolkit.osfile.log", false);
+});
+
+function run_test() {
+  Services.prefs.setBoolPref("toolkit.osfile.log", true);
+
+  run_next_test();
+}
+
+/**
+ * Test OS.File.getAvailableFreeSpace
+ */
+add_task(function() {
+  // Set up profile. We will use profile path to query for available free
+  // space.
+  do_get_profile();
+
+  let dir = OS.Constants.Path.profileDir;
+
+  // Sanity checking for the test
+  do_check_true((yield OS.File.exists(dir)));
+
+  // Query for available bytes for user
+  let availableBytes = yield OS.File.getAvailableFreeSpace(dir);
+
+  do_check_true(!!availableBytes);
+  do_check_true(availableBytes > 0);
+});