Supermarket is a tested code kata which contains Checkout class with the fallowing methodes:
addItemPrice: gets item (string) and price (int) and adds the item and its price to the list of priced items.
addItem: gets item (string) and increments the number of the item by one if its a priced item otherwise throws invalid argument exception
addDiscount: gets item (string), nbrOfItems (int), and discountPrice (int) and adds the discount to the item.
calculateTotal: calculates and returns total (int).