If you work on any NASA manned space program or for a supplier to NASA you must get drug tested. Anyone working in an industry that supplies parts for aircraft is required by the FAA to get drug tested. Not knowledgeable about military contracts but it would surprise me if you worked for a company that had government military contracts that you wouldn't need to be drug tested.
nuke power - entry test, random tests and can be called "for cause" testing any time management thinks you are unfit for duty. same goes for alcohol.