Yeah dude, u have to pass a test with questions like "how many d*cks does a tailed beast have* and "do u dress up as a woman in your spare time?" or "have you ever chased after an emo-boy 24/7?"
in order to be sannin you have to have at least 4300 posts + in naruto test you will fight 1 of these bios against one of the senseis:
1) 4th Raikage
2) Sasuke with MS
3) Itachi and Kisame
4) 6 Paths Of Pain
and even if you beat them, that doesn´t mean you pass + there can only be 1 jinchuuriki bio for each bijuu, meaning that.........most likely before you get to that rank someone already will have him