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);
}