public void TestComboOfferCalculation_extraItems()
        {
            Product productA = new Product();

            productA.productName  = "A";
            productA.productPrice = 50;
            productA.productType  = "clothing";
            productA.discountList = new List <string>();

            ComboOffer productA_Combo = new ComboOffer(productA, 3, 130);
            float      Price          = productA_Combo.calculatePrice(5);

            Assert.AreEqual(230, Price);
        }