Upgrade to test 0.12.0.

test/trailing_options_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 trailing_options_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:args/args.dart';
 
 void main() {
   test('allowTrailingOptions defaults to false', () {
     var parser = new ArgParser();
     expect(parser.allowTrailingOptions, isFalse);
   });
 
   group('when trailing options are allowed', () {
     var parser;
@@ skipping 73 matching lines @@
     var results = parser.parse(['a', '-f', 'b']);
     expect(results['flag'], isTrue);
     expect(results.rest, equals(['a', 'b']));
 
     results = parser.parse(['cmd', '-f', 'a', '-v', '--unknown']);
     expect(results['flag'], isTrue); // Not trailing.
     expect(results.command['verbose'], isFalse);
     expect(results.command.rest, equals(['a', '-v', '--unknown']));
   });
 }