If two Maps are compared with an equals() matcher and they have the same length,

pkg/unittest/test/matchers_test.dart

 // Copyright (c) 2012, 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.
 
 library unittestTests;
 import 'package:unittest/unittest.dart';
 import 'dart:async';
 part 'test_utils.dart';
 
 doesNotThrow() {}
@@ skipping 503 matching lines @@
   group('Map Matchers', () {
 
     test('isEmpty', () {
       var a = new Map();
       shouldPass({}, isEmpty);
       shouldPass(a, isEmpty);
       a['foo'] = 'bar';
       shouldFail(a, isEmpty, "Expected: empty but: was <{foo: bar}>.");
     });
 
+    test('equals', () {
+      var a = new Map();
+      a['foo'] = 'bar';
+      var b = new Map();
+      b['foo'] = 'bar';
+      var c = new Map();
+      c['bar'] = 'foo';
+      shouldPass(a, equals(b));
+      shouldFail(b, equals(c),
+          "Expected: <{bar: foo}> but: missing map key bar 'bar'.");
+    });
+
     test('contains', () {
       var a = new Map();
       a['foo'] = 'bar';
       var b = new Map();
       shouldPass(a, contains('foo'));
       shouldFail(b, contains('foo'),
           "Expected: contains 'foo' but: was <{}>.");
       shouldFail(10, contains('foo'),
           "Expected: contains 'foo' but: was <10>.");
     });
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       var w = new Widget();
       w.price = 10;
       shouldPass(w, new HasPrice(greaterThan(0)));
       shouldFail(w, new HasPrice(greaterThan(10)),
           'Expected: Widget with a price that is a value greater than <10> '
           'but: price was <10>.');
     });
   });
 }