public void RetrievePayments_ShouldReturnSuccessfullPayment_WhenGivenValidIdentifier() { var Identifier = new Guid(); BankPreviousPaymentDetailDTO paymentDetail = new BankPreviousPaymentDetailDTO() { Amount = 100, Currency = "Euro", CardNumber = "1234567891234567", PaymentStatusCode = 200 }; mockPaymentGateService.Setup(x => x.RetrievePreviousPayment(Identifier)).Returns(paymentDetail); _paymentGatewayController = new PaymentGatewayController(mockPaymentGateService.Object); JsonResult paymentInfo = _paymentGatewayController.RetreivePayments(Identifier); }