The first testing (and this was before faith) I did was of the instructions on how to live from Christ, beginning with "love your neighbor as yourself" -- doing it literally with the (until that time) strangers that lived immediately next door to me on both sides. That works spectacularly well, and I thought I must have been sorta lucky and tried it again in new locations, and again it works wonderfully, and I also began testing other things He instructed such as forgiving and even in time trying the radical and unlikely sounding "love your enemy" which was very difficult to do in the first minutes. And worked so well it was just...astounding, These things can be (were for me) like one buys a lottery ticket and it pays $100,000 or something like that. Or 4 tickets, and each pay out amazingly. It just works. Just success after success from these various instructions. That was convincing that Jesus knew very well what He was talking about, far more than I'd imagined or guessed at first, in fact perfectly, and that made me finally begin to wonder about the other things He had said, about God...
See? So I tested that finally, by seeking God. That's the leap of faith, when it's for real. "You will seek me and you will find me when you seek me with all of your heart."
-- It's for real, I found out. So, that was the testing I did. These are things anyone could try. Sometimes I've used a metaphor to say it's sorta (or can be) like leaving the familiar, and sailing into the unknown. It's...a leap of faith.
But before one sails off into uncharted water, they should read the words from the Guide, the one Who knows the way best, Jesus of Nazareth, and listen the best they possibly can. That points you in the right direction.