diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_5/Array/length-truncate-nonconfigurable.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_5/Array/length-truncate-nonconfigurable.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ * Contributor:
+ *   Jeff Walden <jwalden+code@mit.edu>
+ */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 858381;
+var summary =
+  "Array length redefinition behavior with non-configurable elements";
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+var arr = [0, 1, 2];
+Object.defineProperty(arr, 1, { configurable: false });
+
+try
+{
+  Object.defineProperty(arr, "length", { value: 0, writable: false });
+}
+catch (e)
+{
+  assertEq(e instanceof TypeError, true,
+           "must throw TypeError when array truncation would have to remove " +
+           "non-configurable elements");
+}
+
+assertEq(arr.length, 2, "length is highest remaining index plus one");
+
+var desc = Object.getOwnPropertyDescriptor(arr, "length");
+assertEq(desc !== undefined, true);
+
+assertEq(desc.value, 2);
+assertEq(desc.writable, false);
+assertEq(desc.enumerable, false);
+assertEq(desc.configurable, false);
+
+/******************************************************************************/
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("Tests complete");