anchor.diff:    debugger();
     registerExtension('ext..error', Handler);
     registerExtension('ext..exception', Handler);
  -  registerExtension('ext..null', Handler);
  -  registerExtension('ext..nullFuture', Handler);
     registerExtension('ext..success', Handler);
     bool exceptionThrown = false;
     try {
  
positive.code:         'method': method,
          'parameters': paremeters,
        })));
      case 'ext..null':
        return null;
      case 'ext..nullFuture':
        return new Future<ServiceExtensionResponse>.value(null);
    }
  }
  
  
negative.code:       expect(e.message.startsWith('I always throw!\n'), isTrue);
      }
  
      result =
          await isolate.invokeRpcNoUpgrade('ext..success', {'apple': 'banana'});
      expect(result['type'], equals('_extensionType'));
  