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diff --git a/js/src/tests/test262/intl402/DateTimeFormat/subclassing.js b/js/src/tests/test262/intl402/DateTimeFormat/subclassing.js
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+++ b/js/src/tests/test262/intl402/DateTimeFormat/subclassing.js
@@ -0,0 +1,30 @@
+// Copyright 2011-2012 Norbert Lindenberg. All rights reserved.
+// Copyright 2012 Mozilla Corporation. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+es5id: 12.1.2
+description: Tests that Intl.DateTimeFormat can be subclassed.
+author: Norbert Lindenberg
+includes: [compareArray.js]
+---*/
+
+// get a date-time format and have it format an array of dates for comparison with the subclass
+var locales = ["tlh", "id", "en"];
+var a = [new Date(0), Date.now(), new Date(Date.parse("1989-11-09T17:57:00Z"))];
+var referenceDateTimeFormat = new Intl.DateTimeFormat(locales);
+var referenceFormatted = a.map(referenceDateTimeFormat.format);
+
+class MyDateTimeFormat extends Intl.DateTimeFormat {
+  constructor(locales, options) {
+    super(locales, options);
+    // could initialize MyDateTimeFormat properties
+  }
+  // could add methods to MyDateTimeFormat.prototype
+}
+
+var format = new MyDateTimeFormat(locales);
+var actual = a.map(format.format);
+assert.compareArray(actual, referenceFormatted);
+
+reportCompare(0, 0);