Elena is developing an automated ticketing program for a regional eco-railway called GreenRail. The rules of the program are:

• the user selects a travel zone from 1 to 5
• the user enters the number of tickets to purchase (minimum 1, maximum 10)
• if the user has an eco-pass, they input an 8-digit serial number to apply a 20% discount
• if any input is invalid, the system displays an appropriate error message and prompts for reentry.

Complete the table by naming and describing one type of testing (other than unit testing) that should be carried out on Elena's program before it is released to the public.