Not to put any worry in your mind but i actually lost my job on the weekend for failing a drug test, if only i'd known i would've stayed off that day. Since ive lost my job tho everyone i know has suddenly became an expert of cheating drug tests (bit late ha) apparently theres a drink you can get that if you drink an hour before test or something will not get rid of the THC in your system but will mask it making the initial test come up clear, this should then hopefully prevent any other samples of yours being sent off through the "chain of custody" to a laboratory for further analysis, i think they can pretty easily suss out that its been adulterated. I think this would be helpful for the heavy smoker like myself, but if you smoke as little as you say maybe just make yourself a strict regime of drinking HEAVY water and also mixing in alot of pure fruit smoothies (mango, orange and anything anti-oxidating) and after a few days buy a home drug test for your own piece of mind?
Either way pal, all the best and good luck