public void ShouldSumCostOfOrder() { // Arrange var ProductCD = new Product() { Type = ProductType.CD, Name = "Nirvana", Description = "Album" }; var ProductMovie = new Product() { Type = ProductType.DVD, Name = "Gladiator", Description = "Movie" }; var order = new Order() { Items = new List <OrderItem>() { new OrderItem() { Quantity = 1, Price = 10, Product = ProductCD }, new OrderItem() { Quantity = 2, Price = 10, Product = ProductMovie } } }; // Act var actual = OrderHelper.Cost(order); // Assert Assert.AreEqual(30, actual); }