pkg/matcher: refactor with unittest v0.12 work

test/pretty_print_test.dart

 // Copyright (c) 2013, 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.pretty_print_test;
 
 import 'package:matcher/matcher.dart';
 import 'package:matcher/src/pretty_print.dart';
-import 'package:unittest/unittest.dart' show group, test;
+import 'package:unittest/unittest.dart' show group, test, expect;
 
 void main() {
   test('with primitive objects', () {
     expect(prettyPrint(12), equals('<12>'));
     expect(prettyPrint(12.13), equals('<12.13>'));
     expect(prettyPrint(true), equals('<true>'));
     expect(prettyPrint(null), equals('<null>'));
     expect(prettyPrint(() => 12), matches(r'<Closure(: \(\) => dynamic)?>'));
   });
 
@@ skipping 165 matching lines @@
       expect(prettyPrint({'0': 1, '2': 3, '4': 5, '6': 7}, maxItems: 4),
           equals("{'0': 1, '2': 3, '4': 5, '6': 7}"));
     });
 
     test("that's over maxItems", () {
       expect(prettyPrint({'0': 1, '2': 3, '4': 5, '6': 7}, maxItems: 3),
           equals("{'0': 1, '2': 3, ...}"));
     });
   });
 }