There is no standard test to be used. The questions are created by members of the community. To vote/submit/comment, you will need to answer one of these questions chosen at random.
If you don't get it right, you might have to wait an hour or so before trying again with another randomly chosen question. And if you get too many wrong, you would get kicked off the site.
If many members start to see contributions from people who are not that smart, they could try to make their questions tougher. And so you would have a higher probability of receiving a tougher question.
If many members feel that the community is too small, then they might make their questions easier. And so you would have a higher probability of receiving an easier question.