Depends upon how much proof I think I need to see. Both min/max are an hour but you can spend as long as you'd like on some. We take fun problems (github challenge projects I've spent days on just for fun) and give them as tests. We ask you just to spend as much time as you want to give us a sense that you can actually code and give us a sense of your coding style. We're mostly looking that you can 1) actually solve problems 2) write legible code 3) write maintainable code.
We don't give out dumb, tedious quizzes or anything. These are actual projects written to be fun. We don't get many/any complaints.
We also give out the coding test very late in the interview cycle. I'd say we hire 80% of the people we give tests to. We already have a pretty good idea you'll be a good fit by that point. So we're not wasting your time.