BusAirDriver
...and that nicely rounds out the case in that I as both a pilot and a fare paying passenger don't really care whether my pilot flying, is drunk, fatigued, on medication, or on drugs. (Don't mention suicidal)
The test will probably catch it and is not dependent on blood content, time, temperature, amount of sleep or anything else. It only serves to confirm that a level of competency has been achieved in core skills prior to operation.
Whether the tests are 2 minutes, 10 minutes, before first sector, before last sector, short haul, long haul, daily, random or whatever. I think it would be a significant improvement to current procedures.