Upgrade to the new test runner.

test/url_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.
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:path/path.dart' as path;
 
 main() {
   var context = new path.Context(
       style: path.Style.url, current: 'http://dartlang.org/root/path');
 
   test('separator', () {
     expect(context.separator, '/');
   });
 
@@ skipping 741 matching lines @@
 
     test('with a root-relative URI', () {
       expect(context.prettyUri('/a/b'), '/a/b');
     });
 
     test('with a Uri object', () {
       expect(context.prettyUri(Uri.parse('a/b')), 'a/b');
     });
   });
 }