Gift cards
Test mode: payments use the PayPal sandbox – no real money.
Check a gift card
Use a gift card at checkout: enter its code in the "Gift card code" field. If it covers the whole price, no PayPal is needed.
Combine gift cards
Got several gift cards? Put everything on one card: the whole balance of the other cards moves onto it and they are emptied. The combined card keeps the earliest expiry date of the cards (if any has one).