Advice on passing a test.

So I'm a heavy smoker who just quit today. I smoke multiple times a day. I have 45 days to get clean, so I should have enough time, but is there anything I should do to ensure I'll be good?

Is there any chance I could still be dirty after so long, and is there anything I should do or avoid?

I know my brother once popped dirty after a month once, and I think it was due to working out and burning fat cells that had thc, so I'm just trying to be extra certain I'll be good.