CDL Practice Test

Every state is different. Here in Maine the general question test was 15. Airbrake had about 8 questions and hazmat hat 32 questions.
Also the driving test is different in each state. Here in Maine we only had to do a straight back, then a offset pullup, from there to do a parrallel parking and then a street to side door parking.
When I went to drive at CR England ther were drivers that were telling me in their state they had to show the ability to drive in reverse and do a figure 8. Some one else said they had to straight back 300 feet, hook around the side of a building (still in reverse) and go another 300 feet, then blind back to the left for another 300 feet, followed by a second blind back, with one final hook around the side of another building (not certain, I think he said he was from Ohio).

So my advice would be to go to where you get your license and ask for their commercial drivers study book and start reading. What they have here are the generic questions to familiarize you with what is expected.
Mind you this is only for the written. Also required here in Maine was proof you had at least 27 hours driving a truck to get the permanent physical license.