diff -r 000000000000 -r 6474c204b198 toolkit/components/thumbnails/test/browser_thumbnails_bg_no_auth_prompt.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/thumbnails/test/browser_thumbnails_bg_no_auth_prompt.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,21 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// the following tests attempt to display modal dialogs.  The test just
+// relies on the fact that if the dialog was displayed the test will hang
+// and timeout.  IOW - the tests would pass if the dialogs appear and are
+// manually closed by the user - so don't do that :)  (obviously there is
+// noone available to do that when run via tbpl etc, so this should be safe,
+// and it's tricky to use the window-watcher to check a window *does not*
+// appear - how long should the watcher be active before assuming it's not
+// going to appear?)
+function runTests() {
+  let url = "http://mochi.test:8888/browser/browser/base/content/test/general/authenticate.sjs?user=anyone";
+  ok(!thumbnailExists(url), "Thumbnail file should not already exist.");
+
+  let capturedURL = yield bgCapture(url);
+  is(capturedURL, url, "Captured URL should be URL passed to capture.");
+  ok(thumbnailExists(url),
+     "Thumbnail file should exist even though it requires auth.");
+  removeThumbnail(url);
+}