You have been testing a web application that takes airline reservations. There has been a problem that occurs when an existing user logs in and makes a reservation. If they query first, then select a particular flight and confirm the reservation, they are allowed to cancel the reservation. If they don't query but enter a particular flight number, then select it from the matched list, then confirm and try to cancel, the cancel fails. What technique should you use to do further testing and to look for similar issues?