pkg/unittest: give Configuration a default (blank) implementation

pkg/unittest/lib/src/simple_configuration.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.
 
 part of unittest;
 
 // A custom failure handler for [expect] that routes expect failures
 // to the config.
 class _ExpectFailureHandler extends DefaultFailureHandler {
   final SimpleConfiguration _config;
 
   _ExpectFailureHandler(this._config);
 
   void fail(String reason) {
     _config.onExpectFailure(reason);
   }
 }
 
 /**
  * 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
  * this class.
  */
-class SimpleConfiguration implements Configuration {
+class SimpleConfiguration extends Configuration {
   // The VM won't shut down if a receive port is open. Use this to make sure
   // we correctly wait for asynchronous tests.
   ReceivePort _receivePort;
 
   /**
    * Subclasses can override this with something useful for diagnostics.
    * Particularly useful in cases where we have parent/child configurations
    * such as layout tests.
    */
-  final String name = 'Configuration';
+  String get name => 'Configuration';
 
   bool get autoStart => true;
 
   /**
    * If true (the default), throw an exception at the end if any tests failed.
    */
   bool throwOnTestFailures = true;
 
   /**
    * If true (the default), then tests will stop after the first failed
    * [expect]. If false, failed [expect]s will not cause the test
    * to stop (other exceptions will still terminate the test).
    */
   bool stopTestOnExpectFailure = true;
 
   // If stopTestOnExpectFailure is false, we need to capture failures, which
   // we do with this List.
   final _testLogBuffer = <Pair<String, Trace>>[];
 
   /**
    * The constructor sets up a failure handler for [expect] that redirects
    * [expect] failures to [onExpectFailure].
    */
-  SimpleConfiguration() {
+  SimpleConfiguration() : super.blank() {
     configureExpectFailureHandler(new _ExpectFailureHandler(this));
   }
 
   void onInit() {
     _receivePort = new ReceivePort();
     _postMessage('unittest-suite-wait-for-done');
   }
 
-  void onStart() {}
-
   /**
    * Called when each test starts. Useful to show intermediate progress on
    * a test suite. Derived classes should call this first before their own
    * override code.
    */
   void onTestStart(TestCase testCase) {
     assert(testCase != null);
     _testLogBuffer.clear();
   }
 
@@ skipping 127 matching lines @@
       }
     }
   }
 
   void _postMessage(String message) {
     // In dart2js browser tests, the JavaScript-based test controller
     // intercepts calls to print and listens for "secret" messages.
     print(message);
   }
 }