It means that upon success, they then assign you to a truck and you're on your way. Solo. All it is is a skills test. - Cheers.
If you're a great driver somewhere along the line your trainer will say so and you might be able to test out of remaining training period. So you you go back to the yard early and take a skills test. If you pass it you don't have to go back out with the trainer.
It means that your mentor has cleared you to go solo, and you do a road test and a short written test. The road test is basically the same driving test you did in orientation. You drive around the block and do a couple backs in the yard. The written is just as easy.
After testing out you are then assigned a truck. That can take a day or so, and if you are at your home terminal they may be reticent to put you up in a hotel. That happened to me, and it would have been a major pain to get home by bus. I pushed and suddenly they had a truck available. I slept in my truck that night while waiting for my first dispatch.
I didnt have to do a written to test out, I did a "mid term" written where you explain the macros and show you can follow a route and atlas etc, when I tested out I drove around a block then did a single backing