Ive got a potential drug test in 2 weeks, advice please?

I caught wind of the rumor at work and have already been clean a week. I rush ordered the pissinator and have so far done 2 rehersals with it. Today my rehearsal temp was 92 degrees. I weigh 210 lbs and am 5'11. There is a potential that when the test runs I will have been clean for 3.5 weeks. Any advice from anyone who has defeated piss tests with synthetic urine would be appreciated, I hope that by the time of the test I can just go as normal. Any chance I a synthetic can fail?

thanks