Hey I know exactly how you feel. At my first dojo in Japan I wasn`t allowed to grade for 5th que for about a year...and I saw totally incompetent Japanese grading after maybe a month...or even people who hardly came to training (I was there all the time) be allowed to take higher grades
in the end though the colour of your belt means nothing and dedication in training clearly shows on the mat. They can`t take your ability away from you
My situation was different but my advise would be to subtly ask the Sensei which techniques you will need to concentrate on for your first test...what he thinks you might need to work on. This could only help and wouldn`t be taken as being disrespectful i`m sure.
Good luck
Lee