Who needs something else?
Using the nixos framework, tests can be written and performed. See https://nixos.org/manual/nixos/stable/index.html#sec-nixos-tests
Perform all tests using nix flake check. Call a specific test using nix build .#checks.x86_64-linux.test1
nix flake check
nix build .#checks.x86_64-linux.test1
The VM can be build using nixos-rebuild build-vm --flake .#matrix and started using result/bin/run-nixos-vm.
nixos-rebuild build-vm --flake .#matrix
result/bin/run-nixos-vm
See also https://gist.github.com/FlakM/0535b8aa7efec56906c5ab5e32580adf