Fantasy. Apprentice mages in deprivation, must visualize/ remember food that appears from wall, divert ants. Read before 2013. Spoiler.

[Ann]

This was a fantasy book. Scrolling through my GoodReads I didn't see it, so I think I must have read it before 2013. I can't remember if it was YA or adult.

The main character is a boy/teen. He grew up in poverty. Somehow he ends up being trained in the use of magic (can't remember if he knew that was what he was doing?). There are lots of other boys there with him, but the trainers discourage them from making friends with each other. It might be underground? They are fed hardly anything, and they're always cold and hungry.

There is a wall, and the boys can only get food from the wall with magic by both the sheer willpower of really, really wanting it and also by visualizing perfectly the thing, along with a happy memory of the thing. But the boy doesn't have any happy memories surrounding food. I think he finally succeeds with an apple? He may have also summoned a toy horse by remembering stealing it?

Once he passes those tests he goes on to another level of training. This one has something to do with ants. I think maybe there's a trail of honey and he has to use magic to make the ants crawl away from the honey?

There's another test scenario with a snake. Maybe he has to kill the snake before it kills him? Pretty sure his life was in danger, or at least he believed it to be. I think he maybe does something that lets him live but doesn't kill the snake and the trainers are disgusted, but I could be wrong.