The question about the air brake test prior to the test ride is simple. It is just like the examiner giving a test in the family car. They check the headlights,turn signals, W/S wipers, etc. The same applies when you take a drivers test in your bus. They are simply checking for the safety of the bus before you move with them aboard. All test drives must be conducted in a safe and fully functional vehicle.

Some states (like Nevada) require the air brake written test as a separate part of the exam for a Class B.

This site, while not current to this year, gives the RV license requirements for all states.

This whole subject has been discussed ad nauseam on this site and I am sure it will continue since laws change or are not clearly defined. My take on this is if your state requires the license then get it. If it isn't required just make sure you are clearly capable of operating your vehicle safely. In the event of an accident your qualifications to operate the equipment will surely be questioned, not only by the authorities but by a host of lawyers intent of separating you and your insurance company from a lot of money. There is no substitute for good planning.