Since I live outside of my congregation territory, I always try to open deep discussions with the JWs that knock on my door on Saturdays, then after 30 minutes and when I see they are struggling I tell them I am a fellow JW from another congregation that was testing them!
You should see their faces! Some smile and some get really upset that I wasted their time. The interesting thing, none has any deep understanding of the beliefs and most cannot defend using the bible only, they have to go and do some research!
Remember old times when I was a teenager and was supposed to memorise all conversation stoppers and use the bible to defend our beliefs - good old times!