Add a test runner executable.

lib/src/engine.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.
 
 library unittest.engine;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'live_test.dart';
@@ skipping 46 matching lines @@
       _onTestStartedController.add(liveTest);
 
       // First, schedule a microtask to ensure that [onTestStarted] fires before
       // the first [LiveTest.onStateChange] event. Once the test finishes, use
       // [new Future] to do a coarse-grained event loop pump to avoid starving
       // the DOM or other non-microtask events.
       return new Future.microtask(liveTest.run).then((_) => new Future(() {}));
     }).then((_) =>
         liveTests.every((liveTest) => liveTest.state.result == Result.success));
   }
+
+  /// Signals that the caller is done paying attention to test results and the
+  /// engine should release any resources it has allocated.
+  Future close() =>
+      Future.wait(liveTests.map((liveTest) => liveTest.close()));
 }