What is Passive Testing?
Passive testing is a software testing technique that observes the system without interaction. On the other hand, active testing involves interaction with the system.
Active Vs Passive Testing:
Consider a password based authentication system. Password testing is performed to check if the user can login using easy passwords. Upon successful login the program might mail or write a success message the sys admin. This testing is active testing. Passive testing in this case, involves testing of the password file protection and comparing the encrypted strings.