public void callService() { BasePayPalService service = new BasePayPalService("Invoice", "1.7.0"); string response = service.Call("SendInvoice", "requestEnvelope.detailLevel=ReturnAll&requestEnvelope.errorLanguage=en_US&invoiceID=INV2-PCWG-P78G-7EYV-94QY", null); Assert.IsNotNull(response); StringAssert.Contains("responseEnvelope.ack", response); }