public void TestClearPurchases()
{
//arrange
Catering catering = new Catering(fa);
CateringItem[] items = catering.GetInventory();
string code = items[0].ProductCode; //first item
catering.AddMoney("20");
catering.MakePurchase(code, "1");
//act
CateringItem[] purchases = catering.GetPurchases();
//assert
Assert.AreEqual(1, purchases.Length);
//act
catering.ClearPurchases();
purchases = catering.GetPurchases();
//assert
Assert.AreEqual(0, purchases.Length);
}