public void FetchedCustomerDetailsTest()
{
CustomerDetails customerDetails = SetModelData();
string response = "Payment cannot be done";
Mock <IPaymentClient> mock = new Mock <IPaymentClient>();
mock.Setup(g => g.MakePayment(It.IsAny <string>(), It.IsAny <string>())).Returns(response);
PaymentGateway paymentGateway = new PaymentGateway(mock.Object);
string res = paymentGateway.FetchedCustomerDetails(customerDetails);
Assert.IsNotNull(res);
}