Hi guys,
First off, I want to say I appreciate the support you guys provide for your plugin.
This question is one that I’m kind of surprised I haven’t seen asked before, but perhaps that’s for a good reason. Anyways, would you be able to recommend a Wordpress QA testing environment such as XAMPP or WAMP? If not, I understand, as this may not be entirely relatable to S2Member directly, though I suspect that S2Member would work better on some environments rather than others.
Thanks again,
I use Local by Flywheel when I develop locally. I almost always use a dev site on the same hosting provider/server setup that will be used for production, however. I can easily set up a staging site on the same server as the production site in most cases and my internet connection is good (but not great). Local comes in handy when some dummy throws a switch in the DSL box across the street though. 
I use Linux Mint as my desktop (and laptop) operating system, and have done since 2011. This has numerous advantages, in my view.
One of them is that I can develop WordPress sites natively without any need for extraneous software. That is how I do all my WP development.
When I teach WordPress development, almost all the students use Windows or MacOS. In such cases I have them install DesktopServer so that they can develop on their own laptops.
Awesome responses! Thanks!