The RAAF has been randomly drug and alcohol testing for a couple of years now. I've been tested a couple of times myself. I know that it won't necessarily be the same, but it was all pretty well explained at the time.
Basically go with the official, pee in a bottle. The pee is measured for temperature to make sure you haven't brought someone elses with you. Then they drip a bit on a couple of testing strips. You wait a couple of minutes and then lines appear on the tester. Apparently very similar to a pregnancy test. Took about ten minutes.
They did mention what they were testing for, and it was the standard 'cocaine, barbituates etc etc' and alcohol. I asked about over the counter drugs and the tester mentioned something about it depends on the concentration in the pee. From what I gathered the test they gave only showed a positve result if it was over some sort of concentration which would indicate a particular sort of drug.