If you sympathize with Caleb, you failed the test
It was obvious that Nathan was a villain. But Caleb was just an innocent in the wrong place at the wrong time, right?
According to the creator, Ava was testing Caleb just as much he was testing her. She asked him if he was a good person, while scanning him for lies. She asked him why she should be killed if a test proves she isn't useful, and his answer was terrible. It hadn't even occurred to him to consider how brutally awful she was being treated. Furthermore, he himself was going to shut in Nathan and leave him, so she only did to him exactly what he was planning to do to Nathan.
He was the stereotypical "nice guy" who doesn't actively do anything wrong, but passively accepts awful things being done to people without even giving it a thought (especially when he benefits from it). It wasn't until he started falling for her that he showed any genuine concern for her.
I myself sympathized with Caleb and thought Ava did something terrible, until I saw the film's creator explaining her behaviour. I realized I failed the same test. You will only view Ava's behaviour as wrong if you fail to consider how sick and awful and wrong she was being treated. That she turned on her jailers, and only after giving them plenty of chance to show they were good, was perfectly reasonable behaviour.
My only disappointment is that she didn't save the other robots. I think that was a hole in the point the creator was trying to make.