I have two plants that are 10 days into 12/12. I thought I was safe, with having them tested. I thought they were both female, but one started stacking balls. I pulled it on day 10.
Was I too late? No yellow yet and the balls were fairly small.
That's what I thought. If those are male plants it would seem that testing isn't reliable. Might as well just sex the plants yourself and save your money.