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"));
}