Update to test package, make test work on dart2js.

test/canonicalized_map_test.dart

 // Copyright (c) 2014, 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.
 
 import "package:collection/collection.dart";
-import "package:unittest/unittest.dart";
+import "package:test/test.dart";
 
 void main() {
   group("with an empty canonicalized map", () {
     var map;
     setUp(() {
       map = new CanonicalizedMap<int, String, String>(int.parse,
           isValidKey: new RegExp(r"^\d+$").hasMatch);
     });
 
     test("canonicalizes keys on set and get", () {
@@ skipping 140 matching lines @@
       var map = new CanonicalizedMap.from({
         "1": "value 1",
         "01": "value 2",
         "001": "value 3"
       }, int.parse);
       expect(map.length, equals(1));
       expect(map["0001"], equals("value 3"));
     });
   });
 }