public async void Name_Update_length()
        {
            Mock <IFeedRepository> feedRepository = new Mock <IFeedRepository>();

            feedRepository.Setup(x => x.Get(It.IsAny <string>())).Returns(Task.FromResult(new Feed()));

            var validator = new ApiFeedRequestModelValidator(feedRepository.Object);
            await validator.ValidateUpdateAsync(default(string), new ApiFeedRequestModel());

            validator.ShouldHaveValidationErrorFor(x => x.Name, new string('A', 201));
        }
        private async void BeUniqueByName_Update_Not_Exists()
        {
            Mock <IFeedRepository> feedRepository = new Mock <IFeedRepository>();

            feedRepository.Setup(x => x.ByName(It.IsAny <string>())).Returns(Task.FromResult <Feed>(null));
            var validator = new ApiFeedRequestModelValidator(feedRepository.Object);

            await validator.ValidateUpdateAsync(default(string), new ApiFeedRequestModel());

            validator.ShouldNotHaveValidationErrorFor(x => x.Name, "A");
        }