public void TestIsSoldOut()
        {
            //arrange
            Catering catering = new Catering(fa);

            CateringItem[] items = catering.GetInventory();
            string         code  = items[0].ProductCode; //first item

            catering.AddMoney("2000");

            //act
            catering.MakePurchase(code, "50");

            //assert
            Assert.IsTrue(catering.IsSoldOut(code));
        }