The test consists of a black cube about 25cm^3. Inside the cube there is a light (the lantern). On the front of the cube, there are two holes, each approximately the diameter of a ballpoint pen tip. Between the holes and the lantern (inside the box), there is a disc that changes the colour of light to either red, green, or white. There are 25 combinations on the wheel.
The subject sits approx 10 meters away from the box in a darkened room, and stares at the two holes. You are to identify the colour of light emitting from each hole (they are approx. 5 cm apart, horizontally) by indicating "red/white" "green/red" "white/green" etc. or whichever combination thereof. There are 25 combinations allowed on the disc, and it is spun around twice thereby testing you on 50 combinations.
I do not know what the pass mark is out of 50, however I can say that I had to take this test and was very stressed. After the "jitters" wore off you will do fine, as I did! Good luck.