I just recently had to renew mine (Snuck up on me). I took the Class A brakes test and barely passed. It has air brake questions and not going to lie, I know nothing about air brakes. Also the lamp test. They aren't TOO bad, but there are a lot of very specific questions they expect you to know. I highly recommend taking this practice test first. Its a little long, but it'll help you out.
I let my lamp certification expire need to recertify it one of these days I keep my break certification current because at 1 time it was needed when I worked on a fleet of fedex vehicles. Other than something to put on my resume honestly I don't know why I keep it because I actually haven't done a break certification in a long time
ASE Master Certified
Chrysler Master Certified
Sequoia Institute Graduate
20+ year experience