public void ProductSellByQuantity_EmptyTest()
        {
            // arrange
            ProductSellByQuantity p = new ProductSellByQuantity();

            // act
            decimal price = p.getPrice();

            // assert
            Assert.AreEqual(0, price);
        }
        public void ProductSellByQuantity_PriceTest()
        {
            // arrange
            ProductSellByQuantity p = new ProductSellByQuantity
            {
                productId   = 276,
                productName = "Boxes of Cheerios",
                unitPrice   = 6.99m
            };

            p.addQuantity(2);

            //act
            decimal price = p.getPrice();

            // assert
            const decimal expectedPrice = 6.99m * 2;

            Assert.AreEqual(expectedPrice, price);
        }