public void UpdateQuantity_Test(RealTimeInventory inventory, int toUpdate)
        {
            IInventoryServiceCompletedMessage response;

            using (var testHelper = CreateInventoryServiceServer(inventory))
                response = testHelper.UpdateQuantityAsync(inventory, toUpdate).WaitAndGetOperationResult();

            InventoryServiceSpecificationHelper.AssertUpdateQuantity(inventory, toUpdate, response);
        }