I simply keep my old systems and test on them to ensure that my programs work well on them. For example I have a 2009 MBP, a couple of HP notebooks one from 20

I simply keep my old systems and test on them to ensure that my programs work well on them. For example I have a 2009 MBP, a couple of HP notebooks one from 2006 and another about 2012. As for the dev system I prefer a mini-tower with three LCDs.