He's right, it takes any where between two weeks and a month to fully leave your system.

But if you wanna keep blazing, there's a few options you have.

A few days before your test you can start drinking a lot of water mixed with vinegar as well as a lot of cranberry juice. The acid in both helps flush your system. It never fails.

Or, you can go to a pharmacy and buy some Quick Flush or some Readi Clean. They'll clean you're system out.