Definition: "You are gay" is a message that you write and hide. If discovered, the person who reads it next fails the test, and is branded GAY.
For example, if there is a notepad lying around, turn over one page, write YOU ARE GAY on the next page, turn back the front page, then wait. Once discovered, shout, "HA! YOU ARE GAY" at the person discovering.
WARNING. It is possible you may forget about it, and indeed fail the test yourself. If you do this, you are most definitely gay.
Malc: Turns the page on the notepad and discovers message.
Stu: "HA! YOU ARE GAY!
Everyone else in room: Haaaa aha ha ha haaaaa ha.