diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_3/String/regress-392378.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_3/String/regress-392378.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,45 @@
+// |reftest| fails
+/* -*- 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 = 392378;
+var summary = 'Regular Expression Non-participating Capture Groups are inaccurate in edge cases';
+var actual = '';
+var expect = '';
+
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+ 
+  expect = ["", undefined, ""] + '';
+  actual = "y".split(/(x)?\1y/) + '';
+  reportCompare(expect, actual, summary + ': "y".split(/(x)?\1y/)');
+
+  expect = ["", undefined, ""] + '';
+  actual = "y".split(/(x)?y/) + '';
+  reportCompare(expect, actual, summary + ': "y".split(/(x)?y/)');
+
+  expect = 'undefined';
+  actual = "y".replace(/(x)?\1y/, function($0, $1){ return String($1); }) + '';
+  reportCompare(expect, actual, summary + ': "y".replace(/(x)?\\1y/, function($0, $1){ return String($1); })');
+
+  expect = 'undefined';
+  actual = "y".replace(/(x)?y/, function($0, $1){ return String($1); }) + '';
+  reportCompare(expect, actual, summary + ': "y".replace(/(x)?y/, function($0, $1){ return String($1); })');
+
+  expect = 'undefined';
+  actual = "y".replace(/(x)?y/, function($0, $1){ return $1; }) + '';
+  reportCompare(expect, actual, summary + ': "y".replace(/(x)?y/, function($0, $1){ return $1; })');
+
+  exitFunc ('test');
+}