Look, it not like once recreational in a state becomes legal, people that have never consumed, just don't all go out at once and start consuming. A vast majority will just buy at a dispensary instead of their hookup depending on quality, pricing and taxation.
All you have to do to pass a MJ pee test is to drink the juice. You have this in your car and can easily pass on a moments notice.
I've personally known maybe a dozen people who have been on probation, pee test multiple times a week for MJ, and smoked MJ everyday.
Now there are some jobs where you can be spot tested and if your job means anything to you, you won't consume. Or if you are a professional driver, not in a union, and get into an accident. I would say a huge majority of HR departs couldn't care less about what you do on your free time as long as it doesn't continue into your job.
Seems like michigan is a state that has been dragging their feet on getting medical MJ to the patients that need it and are using fear, uncertainty and doubt as the recreational vote is around the corner.