I work in a place where the boss would not bother with random drug testing (the performance requirements of the job would quickly give away a user and get him a for-cause test), but, like Josh's situation, our clients want to see a "drug-free workplace" program in effect.
The concept bothers me personally, but not professionally. I understand the need to be assured that we don't have some tweeker blasting through the work we do, or some stoner burning one at lunch before doing critical work.
It bothers me personally, because it's a presumption of guilt, requiring one to prove innocence, which is the opposite of the American justice system.
It's a catch-22, as there is no present way to tell if one's positive result comes from relaxing Friday night, or from having a "wake and bake" breakfast.
I'm willing to accept it as-is, though. It's a matter of priorities. If smoking a joint on Friday night is worth risking your job, your priorities are wrong for my workplace. If you're in to Meth or Heroin, you have bigger problems than simple priorities. We had one painter's helper who was in to Heroin. He stole about $45K worth of stuff to sell at the scrapyard for maybe $600. Something the boss said somehow got me on the suspect list (I got a public apology for that), so he and I went in for questioning. I think the cops had it figured... He rode in the back of a cop car, and I drove myself to the station for questioning. They put us in adjacent rooms, and left me alone. I got to hear him questioned through the wall, and learned a great deal about him I did not know. In the end, I was only asked one question... I was shown a picture of a stolen part found at a scrapyard, and asked if I could identify it.
This kid's dad then tried to bribe my boss into dropping the charges, so that tells you how he was raised...
So I don't complete the hi-jacking of this topic, I'll add that I, too, have dressed nice/casual for the interview, but always carry all the gear I need to test. I went to one interview, where I was told in advance I would not be testing at that time, but took my stuff anyway. When they found out I had dual-shield experience, they asked me to schedule a test. I told them I only needed a place to change, and could test now. They hired me halfway through the test.
Steve S