I use git and commit configs/setup/scripts/etc. to it. I at least have a road map for how to get everything back this way. Testing this can be difficult, but it really depends on what you care about really.

• Testing my kopia backups of important data? that I manually test every once n’ while.
• Testing if my ZFS setup script is 100% identical to my setup? that’s not that important, as long as I have a general idea I can figure out the gaps and improve the script for the next time around. Obviously, you can spend a lot more time ensuring scripts and what not stays consistent, but it depends on what you care about!

For a lot of my service config, git has always worked well for me and I can go back to older configs if needed. You can get super specific here and save versions in git, then have something update the versions (e.g. WUD)

Most of the books I read are docs on all the fuggin homelab devices & services…wish I had time to read books at this point.