i can’t pass a drug test unless they give me notice

I got hired for a position on the floor at a pharmacy and my manager is already wanting me to do their course or be a pharmacy technician on my first week. She thinks i’m a go getter… I don’t know why I said yes! I don’t want to look suspicious and back out (scared i will get fired from my current position), plus, I really want to do it. But I have to do a drug test. and i’m small like 85 pounds and I am a chronic smoker and only smoke dabs. Will I get to schedule my test like 10 days in advance? or should I get clean female pee and put it in my underwear? Ahh i’m so nervous. I don’t even know where to post this.