the idea of a little test before each promotion is even better
Well, there is no reason you couldn't implement something like a cooking test, just send your sim to the culinary hobby lot and make it so they have to win a contest. They get a plaque and a nice $600 when they do. There is nothing stopping you placing the contest table on some other lot and holding the contest there.
"I dream of a better tomorrow, where chickens can cross the road and not be questioned about their motives." - Unknown