The questions are a mix of HSK materials as well as questions which cover particular points mentioned in the lessons as well as some grammar-oriented questions not found elsewhere. The questions should get more difficult as you do better. The goal is to continue expanding it and making the questions better.
That said, if you don't answer anything incorrectly -- we still will recommend something at the level we think you're at. The reason being that we don't want someone who visits the site and starts the test to end up with nothing to do and no idea of what to do next.
Goal is integrating all of this into a more comprehensive learning system with a stronger sense of grammar and teaching points. We're not there yet, but we are moving towards it. Right now we working on another feature we're hoping to announce next week or the week after.