How do you falsify substrate independence?

Substrate independence is the idea that consciousness can reside on different kinds of physical or digital substrates and isn't exclusive to a biological brain. How do you falsify substrate independence if you cannot directly observe consciousness? I can see taking free will as a given, but should we take it as a given that our uploaded mind is a conscious mind? I'd like to know if my potential new neighbors are P-zombies before I move into the Titan supercomputer.