public void PurchaseServiceBuyProductWorksCorrectly()
{
//These could be mocked out, but since they are simple in memory
//instaces there is no point.
ISessionService sessionService = new InMemorySessionService();
IItemRepository itemRepository = new ItemRepository();
IPurchaseService purchaseService = new PurchaseService(itemRepository, sessionService);
Guid sessionId = Guid.NewGuid();
double initialTallyValue = 2;
sessionService.StoreCurrentTally(sessionId, initialTallyValue);
purchaseService.BuyProduct(sessionId, 1);
Assert.True(sessionService.GetStoredTally(sessionId) == (initialTallyValue - itemRepository.GetItem(1).Price));
}
