public void AmountBetween20and500_UseExpensivePaymentGateway()
{
cheapPaymentGateway.Stub(r => r.DoPayment()).Return(false);
expensivePaymentGateway.Stub(r => r.DoPayment()).Return(true);
CreditCard card = new CreditCard();
card.Amount = 300;
card.CreditCardNo = "2421453325661532";
card.CardHolder = "Aakriti";
card.ExpirationDate = DateTime.MaxValue;
card.SecurityCode = "242";
var response = controller.ProcessPayment(card);
Assert.AreEqual(response.StatusCode, HttpStatusCode.OK);
}