Upgrade to the new test runner.

test/io_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.
 
+@TestOn('vm')
+
 import 'dart:io' as io;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:path/path.dart' as path;
 
 main() {
   group('new Context()', () {
     test('uses the current directory if root and style are omitted', () {
       var context = new path.Context();
       expect(context.current, io.Directory.current.path);
     });
 
     test('uses "." if root is omitted', () {
@@ skipping 29 matching lines @@
       io.Directory.current = path.dirname(dir);
       expect(path.normalize(path.absolute('foo/bar')),
           equals(path.normalize(path.join(dir, '../foo/bar'))));
       expect(path.normalize(path.absolute('foo/bar')),
           equals(path.normalize(path.context.join(dir, '../foo/bar'))));
     } finally {
       io.Directory.current = dir;
     }
   });
 }