public void ShouldRemoveItemFromBasketGivenExistingItemDetails() { //arrange var customerId = 123456789; var itemDetail = new { ProductId = 1234, Quantity = 1 }; var sut = new CustomerBasket(customerId); sut.AddItem(itemDetail.ProductId, itemDetail.Quantity); //act sut.RemoveItem(itemDetail.ProductId); //assert Assert.DoesNotContain(sut.Items, item => item.ProductId == itemDetail.ProductId); }