public void Validate_TransactionReferenceHasNonAlphanumericCharacter_ThrowsException()
        {
            PaymentRequest request = new PaymentRequest()
            {
                Amount               = 15.95m,
                CurrencyCode         = CurrencyCode.Euro,
                ReturnUrl            = new Uri("https://www.github.com"),
                TransactionReference = "&"
            };

            ExceptionAssert.ThrowsAlphanumericValidationException(nameof(request.TransactionReference), () =>
            {
                PaymentRequestValidator.Validate(request);
            });
        }