public void ReturnNoValidationErrorsForAGreenModel()
        {
            // arrange
            ProductModel model = GreenProductModel.Model();

            // act
            IEnumerable <ValidationResult> validationResult =
                model.Validate(new ValidationContext(this));

            // assert
            validationResult.Should().HaveCount(0);
        }
        public void ReturnInValidWhenSizeIsEmpty()
        {
            // arrange
            ProductModel model = GreenProductModel.Model();

            model.Size = string.Empty;

            //act
            IEnumerable <ValidationResult> validationResult =
                model.Validate(new ValidationContext(this));

            //assert
            validationResult.Should().HaveCount(1);
        }