A test done to check whether someone claiming to go fishing has actually gone fishing or if they are having an illicit gay love affair. Simply place a note on the end of their fishing pole asking them to bring back some fish. If they do, the test is negative. If the note is still there at the end of the trip, it is positive. They've been to Brokeback.
"Hey, Dad's been going fishing a lot lately with his friend from work. Do you think something's going on?"