How do you find out if your kid is gay?
Lock him in a closet and if he comes out, he's gay. If not, he's dead straight.
Closet Test
Explanation
This joke plays on the phrase "coming out of the closet" which is used to describe someone publicly acknowledging they are gay. It suggests a ridiculously literal and dangerous method of determining a child's sexuality. The humor derives from the absurdity and dark twist of implying that if the child doesn't come out, they are dead, rather than straight.