When a girl turns up to a male geek's room in the night wearing a jacket and no top. If he notices you're topless or mentions it, he's passed. If he doesn't get that your boobs are out, he has failed the geek test. Bra is optional depending on how much of a geek this guy could be.
Guys can also do this test, obviously without a bra, but it works much better when women do it.
Janey: I tried geek testing that internet geek yesterday. Don't think he noticed :(
Brenda: omg he failed the geek test?!
Janey: I know right!