They want to make sure you can drive a large vehicle in a safe manner. They are expecting a very base level of skill and expect you to miss gears and a need to fine tune all of your skills, including backing. They do expect you to understand how to make proper turns with a trailer and if you miss a gear be able to get back into a proper road gear quickly to prevent an unsafe situation. They are not expecting perfection, but unsafe driving will not be tolerated. They just want a base line they can build on.
P.S Practice making a nice smooth stop in school, this will impress your evaluator.