a === b -> identical(a, b)

tests/language/ordered_maps_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Tests that map literals are ordered.
 
 class OrderedMapsTest {
   static testMain() {
     testMaps(const { "a": 1, "c": 2 }, const { "c": 2, "a": 1}, true);
     testMaps({ "a": 1, "c": 2 }, { "c": 2, "a": 1 }, false);
   }
 
   static void testMaps(map1, map2, bool isConst) {
-    Expect.equals(true, map1 !== map2);
+    Expect.isFalse(identical(map1, map2));
 
     var keys = map1.keys;
     Expect.equals(2, keys.length);
     Expect.equals("a", keys[0]);
     Expect.equals("c", keys[1]);
 
     keys = map2.keys;
     Expect.equals(2, keys.length);
     Expect.equals("c", keys[0]);
     Expect.equals("a", keys[1]);
@@ skipping 44 matching lines @@
 
     values = map1.values;
     Expect.equals(3, values.length);
     Expect.equals(4, values[0]);
   }
 }
 
 main() {
   OrderedMapsTest.testMain();
 }