It depends what their testing for. If their testing for specific compounds, like if they have a banned list, then that answers that question for you. You can just pick out which designers are too similar and dont use those.
I was at a competition recently that tested for "abnormal" test readouts. They went into a chemical explanation of what they were looking for, most of it i didnt understand, but i gues they were generally looking for synthetic test, and any sort of anabolic/androgenic agent. They said they could somehow see if you had chemical compunds in your body that would positivly effect muscle building/test levels.