Need help with this.

Been a smoker for the last 4 years daily, now I have a job opportunity that requires me to take a test, I have not been smoking for the last 2 months and I recently took a test and I still come out positive buy only barely so. A friend a have not seen for the last 6 years is coming to visit and I would like to smoke with him,its just for 2 days, but I fear that if i do all the progrees i made in the last 2 months would be wasted and I would need to start from ground 0 again. If I do smoke would I really start from ground 0 or would it take less time for me to detox again. There is no chance for me to take any other routes as the test is made under supervision, yes that includes the time of taking the sample.