public async Task Remove_InvalidatesCachedCart()
        {
            var shoppingCartService = new MockShoppingCartService
                {
                    RemoveShoppingCartItemDelegate = (s, s1) => Task.FromResult(string.Empty),
                    GetShoppingCartAsyncDelegate = s => Task.FromResult(new ShoppingCart(new Collection<ShoppingCartItem>()) {Id = "first"})
                };
            var eventAggregator = new MockEventAggregator
                {
                    GetEventDelegate = type => new ShoppingCartItemUpdatedEvent()
                };
            var target = new ShoppingCartRepository(shoppingCartService, null, eventAggregator, null, new MockSuspensionManagerState());
            var firstCartReturned = await target.GetShoppingCartAsync();

            await target.RemoveShoppingCartItemAsync("TestShoppingCartItemId");

            shoppingCartService.GetShoppingCartAsyncDelegate = s => Task.FromResult(new ShoppingCart(new Collection<ShoppingCartItem>()) { Id = "second" });
            var secondCartReturned = await target.GetShoppingCartAsync();

            Assert.IsNotNull(firstCartReturned);
            Assert.IsNotNull(secondCartReturned);
            Assert.AreNotSame(firstCartReturned, secondCartReturned);
        }
        public async Task GetShoppingCartAsync_CachesCart()
        {

            var shoppingCart = new ShoppingCart(new Collection<ShoppingCartItem>());
            var shoppingCartService = new MockShoppingCartService()
                {
                    GetShoppingCartAsyncDelegate = s => Task.FromResult(shoppingCart)
                };

            var target = new ShoppingCartRepository(shoppingCartService, null, null, null, new MockSuspensionManagerState());
            var firstCartReturned = await target.GetShoppingCartAsync();
            shoppingCartService.GetShoppingCartAsyncDelegate = s =>
            {
                Assert.Fail("Should not have called proxy second time.");
                return Task.FromResult((ShoppingCart)null);
            };

            var secondCartReturned = await target.GetShoppingCartAsync();
            Assert.AreSame(shoppingCart, firstCartReturned);
            Assert.AreSame(shoppingCart, secondCartReturned);
        }