Depends on the type of marijuana use. One single use of marijuana is detectable for about a week. However, long term heavy chronic use causes the break down products to accumulate in the fat and they come out sporadically for up to a few months after completely stopping. But even inthose who have this occur, it does not occur all the time after a month; just sometimes. So, worst case scenario there is quite a good chance you passed. And if you did not use marijuana heavily at past one month is is quite likely you would pass.