Nail the fucker to a church door.
That normally sorts out the truly pious from the pretenders.
(Audioduck So, can I haz fucking Cheezburgers or not?, Fri 22 May 2009, 12:31, archived)

then what do you do with the ones who pass?

( Moon Girl Technologies horrendous beanbag, Fri 22 May 2009, 12:32, archived)