public void Should_Have_Error_When_MerchantId_Is_Null()
            {
                var getCustomerTokensRequest = new MarkByIDRequest
                {
                    MerchantKey = null
                };

                _validator.ShouldHaveValidationErrorFor(x => x.MerchantKey, getCustomerTokensRequest);
            }
            public void Should_Have_Error_When_TransactionID_Is_Null()
            {
                var markByIDRequest = new MarkByIDRequest
                {
                    IDTransaction = null
                };

                _validator.ShouldHaveValidationErrorFor(x => x.IDTransaction, markByIDRequest);
            }