A table knife is more reliable tester than a what is essentially a thick pin, which could easily be wiped clean by the exposed dry cake surface.

The knife will do no damage at all to a cake made with a batter. In any event, anything in a bundt pan will be flipped over and the knife slit hidden from view.

If your round pan has any kind of molded decoration built into it, make sure you are not cheap with greasing it (even if the instructions don't call for it) or it'll be a biatch to get out.