diff -r 000000000000 -r 6474c204b198 testing/xpcshell/example/unit/test_do_get_tempdir.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/testing/xpcshell/example/unit/test_do_get_tempdir.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,16 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* This tests that do_get_tempdir returns a directory that we can write to. */
+
+const Ci = Components.interfaces;
+
+function run_test() {
+  let tmpd = do_get_tempdir();
+  do_check_true(tmpd.exists());
+  tmpd.append("testfile");
+  tmpd.create(Ci.nsIFile.NORMAL_FILE_TYPE, 600);
+  do_check_true(tmpd.exists());
+}