public void Setup()
        {
            _repository = MockRepository.GenerateMock<IStudentRepository>();
             _studentValidator = MockRepository.GenerateMock<IStudentValidator>();
             _studentValidator.Stub(d => d.Validate(Arg<Student>.Is.NotNull))
            .Return(true);

             _studentService = new StudentRegistrationSerivce(_repository, _studentValidator);
        }