diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_5/Array/regress-311515.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_5/Array/regress-311515.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,20 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 311515;
+var summary = 'Array.sort should skip holes and undefined during sort';
+var actual = '';
+var expect = '';
+
+printBugNumber(BUGNUMBER);
+printStatus (summary);
+
+var a = [, 1, , 2, undefined];
+
+actual = a.sort().toString();
+expect = '1,2,,,'; 
+
+reportCompare(expect, actual, summary);