public async Task ProcessFormAsync_UsesExistingIfMatchingFound()
        {
            var newPaymentMethod = new PaymentMethod
            {
                CardNumber = "1234",
                CardholderName = "testcardholdername"
            };

            var existingPaymentMethods = new List<PaymentMethod>
                                        {
                                            new PaymentMethod
                                                {
                                                    Id = "testId",
                                                    CardNumber = "1234",
                                                    CardholderName = "testcardholdername"
                                                }
                                        };

            var checkoutDataRepository = new MockCheckoutDataRepository();
            checkoutDataRepository.GetAllPaymentMethodsAsyncDelegate =
                () => Task.FromResult<ICollection<PaymentMethod>>(new ReadOnlyCollection<PaymentMethod>(existingPaymentMethods));

            var target = new PaymentMethodUserControlViewModel(checkoutDataRepository);
            target.PaymentMethod = newPaymentMethod;

            await target.ProcessFormAsync();

            Assert.AreEqual("testId", target.PaymentMethod.Id);
        }
        public async Task ProcessFormAsync_SavesPaymentMethodIfNoMatchingFound()
        {
            var savePaymentMethodCalled = false;
            var newPaymentMethod = new PaymentMethod
            {
                CardNumber = "1234",
                CardholderName = "testcardholdername"
            };

            var existingPaymentMethods = new List<PaymentMethod>();
            var checkoutDataRepository = new MockCheckoutDataRepository();
            checkoutDataRepository.GetAllPaymentMethodsAsyncDelegate =
                () => Task.FromResult<ICollection<PaymentMethod>>(new Collection<PaymentMethod>(existingPaymentMethods));

            checkoutDataRepository.SavePaymentMethodAsyncDelegate = paymentMethod =>
            {
                savePaymentMethodCalled = true;
                Assert.AreEqual("testcardholdername",
                                paymentMethod.CardholderName);
                return Task.Delay(0);
            };
            var target = new PaymentMethodUserControlViewModel(checkoutDataRepository);
            target.PaymentMethod = newPaymentMethod;

            await target.ProcessFormAsync();

            Assert.IsTrue(savePaymentMethodCalled);
        }