This test is very simple, and in its current incarnation, is very quick. All you have to do is look at a picture, decide whether or not the picture is of a boy or girl, choose your answer, and move on.
Some of these people are dressed in a way that suggests their gender in a traditional way, and others are dressed to subvert expectation.
To avoid hairiness (no pun), I've tried to use pictures of people who identify publicly as one gender or another, so there shouldn't be any trick questions. The people in this quiz identify as 'him' or 'her'. You tell ME which is which.