The internals of the test framework are pretty heavily tied to Nix and NixOS, so a release independent of Nix(OS) isn't probably going to happen. With that said

The internals of the test framework are pretty heavily tied to Nix and NixOS, so a release independent of Nix(OS) isn't probably going to happen. With that said, the test infrastructure itself is exposed as library functions that any Nix user can use. And even though the test VMs itself will run NixOS, the host machine can be any Linux distro with Nix installed.