public void TestCaseCart3()
        {
            //A = 3, B = 5, C = 1, D = 1
            PromotionEngine promotionEngine = new PromotionEngine();

            FillCartList3(promotionEngine);
            decimal orginalPrice = 335m, expectedPrice = 280m;

            (decimal actualPrice, decimal promoPrice) = promotionEngine.PromoCalculator();

            Assert.AreEqual(orginalPrice, actualPrice);
            Assert.AreEqual(expectedPrice, promoPrice);
        }