Add a LoadSuite class.

lib/src/backend/invoker.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 test.backend.invoker;
 
 import 'dart:async';
 
 import 'package:stack_trace/stack_trace.dart';
 
@@ skipping 50 matching lines @@
   ///
   /// This provides a view into the state of the test being executed.
   LiveTest get liveTest => _controller.liveTest;
   LiveTestController _controller;
 
   /// Whether the test has been closed.
   ///
   /// Once the test is closed, [expect] and [expectAsync] will throw
   /// [ClosedException]s whenever accessed to help the test stop executing as
   /// soon as possible.
-  bool get closed => _closed;
-  bool _closed = false;
+  bool get closed => _onCloseCompleter.isCompleted;
+
+  /// A future that completes once the test has been closed.
+  Future get onClose => _onCloseCompleter.future;
+  final _onCloseCompleter = new Completer();
 
   /// The test being run.
   LocalTest get _test => liveTest.test as LocalTest;
 
   /// The test metadata merged with the suite metadata.
   final Metadata metadata;
 
   /// The outstanding callback counter for the current zone.
   OutstandingCallbackCounter get _outstandingCallbacks {
     var counter = Zone.current[this];
@@ skipping 10 matching lines @@
     return Zone.current[#test.invoker];
   }
 
   /// The timer for tracking timeouts.
   ///
   /// This will be `null` until the test starts running.
   Timer _timeoutTimer;
 
   Invoker._(Suite suite, LocalTest test)
       : metadata = suite.metadata.merge(test.metadata) {
-    _controller = new LiveTestController(suite, test, _onRun, () {
-      _closed = true;
-    });
+    _controller = new LiveTestController(
+        suite, test, _onRun, _onCloseCompleter.complete);
   }
 
   /// Tells the invoker that there's a callback running that it should wait for
   /// before considering the test successful.
   ///
   /// Each call to [addOutstandingCallback] should be followed by a call to
   /// [removeOutstandingCallback] once the callbak is no longer running. Note
   /// that only successful tests wait for outstanding callbacks; as soon as a
   /// test experiences an error, any further calls to [addOutstandingCallback]
   /// or [removeOutstandingCallback] will do nothing.
@@ skipping 128 matching lines @@
         // Use the invoker as a key so that multiple invokers can have different
         // outstanding callback counters at once.
         this: outstandingCallbacksForBody
       },
           zoneSpecification: new ZoneSpecification(
               print: (self, parent, zone, line) => _controller.print(line)),
           onError: _handleError);
     });
   }
 }