public void RegisterHandler_Generic_Test() { object parameterObject = new object(); bool handlerExecuted = false; var handler = new Action <object>(o => { handlerExecuted = o == parameterObject; }); testObj.RegisterHandler(handler); var captor = new ArgumentCaptor <Action <object> >(); Verify(handlersByType).TryAdd(Eq(typeof(object)), captor.GetParameter()); VerifyNoMoreInteractions(); AssertFalse(handlerExecuted); captor.Value(parameterObject); AssertTrue(handlerExecuted); }