Add a LiveSuite class.

test/runner/pub_serve_test.dart

 // Copyright (c) 2015, 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")
+@Tags(const ["pub"])
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:scheduled_test/descriptor.dart' as d;
 import 'package:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:test/src/util/exit_codes.dart' as exit_codes;
 
@@ skipping 288 matching lines @@
 
     var test = runTest(['--pub-serve=54321', 'my_test.dart']);
     test.stdout.expect(containsInOrder([
       '-1: loading my_test.dart',
       'Failed to load "my_test.dart": When using "pub serve", all test files '
           'must be in test/.'
     ]));
     test.shouldExit(1);
   });
 }