Unit test changes:

pkg/unittest/lib/src/config.dart

 // Copyright (c) 2011, 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.
 
 part of unittest;
 
 /**
  * Hooks to configure the unittest library for different platforms. This class
  * implements the API in a platform-independent way. Tests that want to take
  * advantage of the platform can create a subclass and override methods from
@@ skipping 34 matching lines @@
   }
 
   /** Called as soon as the unittest framework starts running. */
   void onStart() {}
 
   /**
    * Called when each test starts. Useful to show intermediate progress on
    * a test suite.
    */
   void onTestStart(TestCase testCase) {
+    assert(testCase != null);   
+    assert(_currentTestCase == null);
     _currentTestCase = testCase;
   }
 
   /**
    * Called when each test is completed. Useful to show intermediate progress on
    * a test suite.
    */
   void onTestResult(TestCase testCase) {
+    assert(testCase != null);   
+    assert(_currentTestCase == null || _currentTestCase == testCase);
     _currentTestCase = null;
   }
 
   /**
    * Can be called by tests to log status. Tests should use this
    * instead of print. Subclasses should not override this; they
    * should instead override logMessage which is passed the test case.
    */
   void logMessage(String message) {
     if (currentTestCase == null || _currentTest >= _tests.length ||
@@ skipping 84 matching lines @@
   // Currently e.message works in dartium, but not in dartc.
   handleExternalError(e, String message) =>
       _reportTestError('$message\nCaught $e', '');
 
   _postMessage(String message) {
     // In dart2js browser tests, the JavaScript-based test controller
     // intercepts calls to print and listens for "secret" messages.
     print(message);
   }
 }