 <p>Understanding that you're probably talking about a local/desktop machine and would probably like to <em>continue</em> talking about a local/desktop machine, I'll throw an alternative out there for you just in case it might help you or someone else:</p> <p>Set up multiple virtual server instances in the cloud, and share your code between them as a git repository (or mercurial, I suppose, though I have no personal experience all you really need is something decentralized). This has the benefit of giving you as close to a production experience as possible, and if you have experience setting up servers then it's not that complicated (or expensive, if you just want to spin a server up, do what you need to do, then spin it down again, then you're talking about a few cents up to say 50 cents, up to a few bucks if you just leave it running).</p> <p>I do all of my project development in the cloud these days and I've found it much simpler to manage the infrastructure than I ever did when using local/non-virtualized installs, and it makes this sort of side-by-side scenario fairly straight forward. I just wanted to throw the idea out there if you hadn't considered it.</p>