Game developer looking for a development Mac

I am working on a 2D game, and need a Mac to develop/test our game on. I've considered a Mac Mini, since I can plug in my monitor/mouse/keyboard to it and it's the cheapest option, but they haven't been updated since 2014 I believe. I've been waiting for Apple to announce new Mac Minis for this purpose, but I've been waiting for a very long time now.

So, are 2014 Mac Minis powerful enough to run games? Decent OpenGL support etc. Or should I put down a lot more money for an iMac or a Macbook?

As a personal computer, I'm mostly a Linux & Windows user so I don't know if I would prefer to own a Macbook over a Thinkpad with Linux.