Testing builds?

So. I have build ideas that I don't see on mobafire and I was wondering if there's like a test server or private server where I could say make a bot game where everyone is already 18 and items are free so I can actually test the validity of a build without spending an hour in a custom game farming to buy it, and more farming if it ends up being subpar or I want to tweak it. I've looked at lists of private servers but they all seem to cater to people that want things without playing the game, and I just want to be able to test builds without spending an hour doing so or risk it being crappy in an actual match and costing the round.