For an ATM banking project introduced earlier, "When the user first inserts a valid credit card type, the system considers the user to be in an unauthenticated state. When requesting a cash advance, the user must be in an authenticated state. The user authenticates by entering the proper PIN code. When authenticating the user, the system shall allow the user to enter their PIN code up to three times before failing the authentication and rejecting the card. On the first and second try, the system shall prompt the user to re-enter the PIN code." Suppose you are concerned that, depending on the exact number of invalid PIN codes entered, the system might behave improperly. Which of the following test design techniques is specifically targeted at such failures?