direnv is a useful tool to automatically set environment variables per
project and it also has a nix integration!
I've recently installed my personal laptop to NixOS. Long time i3 user I took this opportunity to use sway instead. To manage some of my home configuration files I'm using the excellent home-manager project.
So you have deployed a NixOS server and want to test a configuration change. How cool would it be to test it locally before sending it over the wire and hope for the best? Well NixOS provides an easy way to start a local VM using your server configuration...