public void Purchase_Test(RealTimeInventory inventory, uint toPurchase)
        {
            IInventoryServiceCompletedMessage response;

            using (var testHelper = CreateInventoryServiceServer(inventory))
            {
                response = testHelper.PurchaseAsync(inventory, (int)toPurchase).WaitAndGetOperationResult();
            }

            InventoryServiceSpecificationHelper.AssertPurchase(inventory, toPurchase, response);
        }