i think you'd be ok to smoke.. there aren't many jobsites that REALLY want to waste their time and money drug testing their employees when they could be doing actual WORK... in many cases, your employer would even give you 24 hours to take care of it, and that's plenty of time to start dilluting (for an infrequent smoker like yourself) or to grab some quick fix 4.0...

of course, it's a decision that is ultimately up to you.. just saying that if it were me, i wouldn't let random drug testing deter me from doing something that i love to do.

respect.