I don't know, there has only been one time that I was tested. I had left something on the counter to cool and one of my cats got up and ate part of it. I took a spoon and scooped out the area where he had eaten LOL.
I have learned that if something need to be left out to cool a bit, it needs to be put in the oven or microwave where the cats can't get to it. The thought of eating after my cats grosses me out but like others have said, I kiss them all the time so I don't know why it would bother me. A psychological thing I guess.
I think a more intriguing question is: would you feed guests
something you knew your cat had taste-tested?
Don't answer that question. My intent is not to hijack this thread, just noting something that crossed my mind.