An employer should have a written drug testing policy that includes:
Links
[1] http://www.shrm.org/legalissues/stateandlocalresources/pages/employers-heroin-epidemic.aspx
[2] http://rethinkpot.org/tags/employer
[3] http://rethinkpot.org/tags/drug-testing
[4] http://rethinkpot.org/tags/drug-free-workplace