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

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

            //assert
            Assert.IsTrue(catering.IsProductValid(code));

            //assert - assume Z1 is not a vaild code
            Assert.IsFalse(catering.IsProductValid("Z1"));
        }