public RedirectToRouteResult RemoveFromCart(Cart cart, int PizzaId, string returnUrl)
        {
            Pizza pizza = repository.Pizzas.FirstOrDefault(p => p.PizzaId == PizzaId);

            if (pizza != null)
            {
                cart.RemoveLine(pizza);
            }
            return RedirectToAction("Index", new { returnUrl });
        }
        public void CanRemoveLine()
        {
            //Arrange
            Pizza p1 = new Pizza { PizzaId = 1, Name = "Pizza1" };
            Pizza p2 = new Pizza { PizzaId = 2, Name = "Pizza2" };
            Pizza p3 = new Pizza { PizzaId = 3, Name = "Pizza3" };
            Cart cart = new Cart();

            //Action
            cart.AddItem(p1, 1);
            cart.AddItem(p2, 2);
            cart.AddItem(p1, 5);
            cart.AddItem(p3, 3);
            cart.RemoveLine(p1);

            //Assert
            Assert.AreEqual(cart.Lines.Count(), 2);
            Assert.AreEqual(cart.Lines.Where(p => p.Pizza == p1).Count(), 0);
        }