I don't think personal testimonies are useless
I meant they are useless for the purposes of reaching any kind of certainty about which religion is the right one. Sure, the more time you spend with a person of faith the more likely you may be to become convinced that there's something to it, but there's something to a lot of things and we don't live long enough to spend the requisite amount of time with representatives of all the worlds many religions in order to determine which something there is more to.