pkg/matcher: upgrate tests to test

test/iterable_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 matcher.iterable_matchers_test;
 
 import 'package:matcher/matcher.dart';
-import 'package:unittest/unittest.dart' show test, group;
+import 'package:test/test.dart' show test, group;
 
 import 'test_utils.dart';
 
 void main() {
   test('isEmpty', () {
     shouldPass([], isEmpty);
     shouldFail([1], isEmpty, "Expected: empty Actual: [1]");
   });
 
   test('isNotEmpty', () {
@@ skipping 159 matching lines @@
         "Actual: SimpleIterable:[]");
   });
 
   test('contains', () {
     var d = new SimpleIterable(3);
     shouldPass(d, contains(2));
     shouldFail(d, contains(5), "Expected: contains <5> "
         "Actual: SimpleIterable:[3, 2, 1]");
   });
 }