diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug513898-regexp.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug513898-regexp.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,51 @@
+/* 
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ * Contributor: haytjes <hv1989@gmail.com>
+ */
+
+/* Check the undefined pattern is equivalent to empty string. */
+
+assertEq(RegExp(undefined).source, '');
+assertEq(RegExp(undefined).global, false);
+assertEq("test".replace(RegExp(undefined), "*"), '*test');
+assertEq(new RegExp(undefined).source, '');
+assertEq(new RegExp(undefined).global, false);
+assertEq('test'.replace(new RegExp(undefined), "*"), '*test');
+
+/* Global flags. */
+
+assertEq(new RegExp(undefined, "g").global, true);
+assertEq("test".replace(new RegExp(undefined, "g"), "*"), "*t*e*s*t*");
+assertEq(RegExp(undefined, "g").global, true);
+assertEq("test".replace(RegExp(undefined, "g"), "*"), "*t*e*s*t*");
+
+/* Undefined flags. */
+
+var re = new RegExp(undefined, undefined);
+assertEq(re.multiline, false);
+assertEq(re.global, false);
+assertEq(re.ignoreCase, false);
+
+var re = new RegExp("test", undefined);
+assertEq(re.multiline, false);
+assertEq(re.global, false);
+assertEq(re.ignoreCase, false);
+
+/* Flags argument that requires toString. */
+
+function Flags() {};
+
+Flags.prototype.toString = function dogToString() { return ""; }
+
+var re = new RegExp(undefined, new Flags());
+assertEq(re.multiline, false);
+assertEq(re.global, false);
+assertEq(re.ignoreCase, false);
+
+Flags.prototype.toString = function dogToString() { return "gim"; }
+
+var re = new RegExp(undefined, new Flags());
+assertEq(re.multiline, true);
+assertEq(re.global, true);
+assertEq(re.ignoreCase, true);