Best way to setup a development test site

I searched the WPMU.org blog and came across this article - https://premium.wpmudev.org/blog/10-ways-to-set-up-a-testing-environment-for-wordpress/

Seemed to be exactly what I was looking for as I'm developing a MU network so DeployMint seemed like a good fit until I saw that the developer isn't supporting it anymore.

How are the good'ol folks here testing out plugins and themes on a WPMU installation before setting them live?

Thanks!
Jeff