I don't know anything about ' testing lists'. For our gradings we have to do a minimum number of training sessions before each grading (increasing number of sessions as you go through the ranks). It is left up to each individual to decide when they want to do another grading, ie: when they think they are ready. We informally mention to our regular sensei that we are thinking about doing a grading the next time there will be an examination (usually a few months before). Also, the senseis will regularly ask a few months before a grading date "Is anyone thinking of doing a grading?". They will then keep an eye on those interested and help you to prepare for it. Of course, they will also let you know if they don't think you are quite ready. Our regular sensei has to sign the application form to indicate that they think you are ready.
Most people have a pretty good idea of how ready they are and don't have to be advised not to go for a grading. Beginners have to rely on their senseis' opinions though. I guess the thinking at my dojo is that people are expected to self-assess as they gain experience. By that I mean a person is encouraged to develop and rely on their own judgment rather than others'.
I should also mention that all of our members are adults.
I think you should ask why you are not being encouraged to do a grading. If you are doing something incorrectly it should have been brought to your attention before this. Why are you asking the senior students questions and not your sensei anyway? I would get together with some others with your concerns and approach your sensei after training and ask him/her to explain the system "when you have got time".