Upgrade to the new test runner.

test/refactor_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 polymer.test.refactor_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:source_maps/refactor.dart';
 import 'package:source_maps/parser.dart' show parse, Mapping;
 import 'package:source_span/source_span.dart';
 
 main() {
   group('conflict detection', () {
     var original = "0123456789abcdefghij";
     var file = new SourceFile(original);
 
     test('no conflict, in order', () {
@@ skipping 122 matching lines @@
         "line 5, column 1: \n"
         "abcd*fghij\n"
         "^");
   });
 }
 
 String _span(int line, int column, Mapping map, SourceFile file) {
   var span = map.spanFor(line - 1, column - 1, files: {'': file});
   return span == null ? null : span.message('').trim();
 }