anchor.diff:      MockHttpServer server;
       MockRequestNavigator requestNavigator;
       MockRouter router;
  -    MockHMAC hmac;
       HttpBodyHandlerMock httpBodyHandler;
   
       setUp(() {
         server = new MockHttpServer();
         router = new MockRouter();
         requestNavigator = new MockRequestNavigator();
  -      hmac = new MockHMAC();
         httpBodyHandler = new HttpBodyHandlerMock();
   
  -      backend = new Backend.config(server, router, requestNavigator, hmac, httpBodyHandler.processRequest);
  +      backend = new Backend.config(server, router, requestNavigator, ()=>new MockHMAC(), httpBodyHandler.processRequest);
       });
   
       test('addRoute', () {
  
positive.code:       });
      });
  
    });
  }
  
  
negative.code: class MockHttpServer extends Mock implements HttpServer {}
  class MockRouter extends Mock implements Router {}
  class MockRequestNavigator extends Mock implements RequestNavigator {}
  class MockHMAC extends Mock implements HMAC {
    var listOfInt = [];
    MockHMAC();
    add(List<int> val) => listOfInt.addAll(val);
    close() => listOfInt.map((int i) => i+10).toList();
    verify(List<int> digest) {
      if (digest.length != listOfInt.length) return false;
        for(int i = 0 ; i < digest.length; i++)
          if (digest[i] != listOfInt[i]+10) return false;
      return true;
    }
  }
  
  class HttpBodyMock extends Mock implements HttpBody {}
  
  class HttpResponseMock extends Mock implements HttpResponse{
  