I'm not going to give you an exact time as to when you will test clean again. The variables are too stretched and there's too many dependants (approximately one week to a few months). As for dependants: Depends on how long you've been smoking, how much you've been smoking, ect. So from personal experiences with drug tests I'll give you some advice and suggest SURE-JELL. I'm not going to give you any scientific reasons why it might or might not work. I mean... let's be real.. nobody
really knows, nor do I feel like it being explained to me. But I will give you the website if you're curious.
http://www.kraftfoods.com/surejell/sj_index.html
It's fruit pectin and helps flush out bodily fluids (not harmful). You will piss alot when you eat it and also might cause some runny-poo.
edit: Also I just mix it with water and chug it a day before a drug test and an hour before the drug test for safety. It's never failed me. But another tip: when you're getting tested substitute every drink for water. It's just one of the things you have to do. I do it 'cause it makes me feel safer. And I would go smoking out a day before the test either... well I'll just stop here and assume you're not retarded.