[ajryan]

Card testing doesn’t require a purchase, fraudsters can validate a card by adding it to an online wallet. The retailer will send a $0 authorization to the bank.

Fraud happens across all transaction amounts, what do you think people use the cards for once they buy or guess a valid card?

[__float]

$0 authorizations are routinely skipped, though - the fees add up substantially because of card testing, some card networks don't support it (and instead you need $1 or similar), and it can be confusing for customers.