It depends on what you're studying for. For my Ruby on Rails position, I revised my Ruby with two books I can't recall right now, but then I spent so much time

It depends on what you're studying for. For my Ruby on Rails position, I revised my Ruby with two books I can't recall right now, but then I spent so much time on codewars.com, because I knew I was going to get tested. Could you share doctrine specifics about your interview? What stack do you work with?