Replying to the original post:
Well if you want to test your fighting skills and pick a fight it's very simple, don't ask
you have a wide range, you can go from your little 8 year old cousin to insulting a bunch of hooligans.
But you always will be asking the same question to yourself all over again. You always will want to know how far you can go... and maybe the "limit" will be the day you "lose". And losing in a fight for real with no rules.. it can be death or serious injuries, perhaps ending handicapped.
I think Aikido is a very difficult martial art, and you have to really master the basics before testing your Aikido for real.. if don't, you will be testing only some fighting skills.
But... you can test your Aikido in ... "testings"... that's what testing goal is, to test your Aikido.