///<summary>
 ///</summary>
 ///<param name="payPalCredentials"></param>
 ///<exception cref="ArgumentNullException"></exception>
 public PayPalNvpPaymentGateway(PayPalCredentials payPalCredentials)
 {
     if (payPalCredentials == null) throw new ArgumentNullException("payPalCredentials");
     this.payPalCredentials = payPalCredentials;
 }
 public void Api_Exploration_Test()
 {
     var payPalCredentials = new PayPalCredentials("username", "password", "signature");
     var payPalNvpPaymentGateway = new PayPalNvpPaymentGateway(payPalCredentials);
     payPalNvpPaymentGateway.Purchase("REF", 100m, "USD", new PaymentCard()).ShouldNotBeNull();
 }