You can run tests using nix-build. For example, to run the test login.nix, you just do: $ nix-build '<nixpkgs/nixos/tests/login.nix>' or, if you don’t want to rely on NIX_PATH: $ cd /my/nixpkgs/nixos/tests $ nix-build login.nix … running the VM test script machine: QEMU running (pid 8841) … 6 out of 6 tests succeeded After building/downloading all required dependencies, this will perform a build that starts a QEMU/KVM virtual machine containing a NixOS system. The virtual machine mounts the Nix store of the host; this makes VM creation very fast, as no disk image needs to be created. Afterwards, you can view a pretty-printed log of the test: $ firefox result/log.html The test itself can be run interactively. This is particularly useful when developing or debugging a test: $ nix-build nixos/tests/login.nix -A driver $ ./result/bin/nixos-test-driver starting VDE switch for network 1 > You can then take any Perl statement, e.g. > startAll > testScript > $machine->succeed("touch /tmp/foo") The function testScript executes the entire test script and drops you back into the test driver command line upon its completion. This allows you to inspect the state of the VMs after the test (e.g. to debug the test script). To just start and experiment with the VMs, run: $ nix-build nixos/tests/login.nix -A driver $ ./result/bin/nixos-run-vms The script nixos-run-vms starts the virtual machines defined by test. The root file system of the VMs is created on the fly and kept across VM restarts in ./hostname.qcow2.