public void Order_SavesOrder()
{
//Arrange
var product = _service.GetAvailableProducts(_order).First();
const int quantity = 1;
_order.AddLineItem(quantity, product);
OrderDto dto = null;
_repo.Setup(repo => repo.CreateOrder(It.IsAny <OrderDto>()))
.Callback <OrderDto>(x => dto = x);
//Act
_service.SubmitOrder(_order);
//Assert
dto.ShouldNotBeNull();
dto.Customer.ShouldBe(_customer);
dto.TotalPrice.ShouldBe(_order.TotalPrice);
dto.LineItems.Count.ShouldBe(1);
var lineItem = dto.LineItems.Single();
lineItem.Product.ShouldBe(product);
lineItem.Quantity.ShouldBe(quantity);
}