I'm not a fan of drug testing. I've seen people come to work with hangovers, but would be considered "Sober" yet their performance was definitely impaired. A mechanical/dexterity and reaction test would be a better indicator of a persons ability to do tasks. (Lance Armstrong passed over 500 drug tests yet he was using PED's throughout his career.) Drug tests are a money maker for prohibitionists.
In any event, nothing justifies the caging of nearly a million Americans a year for using a substance which has been proven to be safe than ones which are currently legal.
The Henningfield-Benowitz substance comparison charts
Nicotine. Cocaine. Caffeine. Marijuana. Benowitz. Henningfield. Less < Addict