The test itself can be run interactively. This is particularly useful when developing or debugging a test: $ nix-build . -A nixosTests.login.driverInteractive $ ./result/bin/nixos-test-driver [...] >>> You can then take any Python statement, e.g. >>> start_all() >>> test_script() >>> machine.succeed("touch /tmp/foo") >>> print(machine.succeed("pwd")) # Show stdout of command The function test_script 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).

You can re-use the VM states coming from a previous run by setting the --keep-vm-state flag. $ ./result/bin/nixos-test-driver --keep-vm-state The machine state is stored in the $TMPDIR/vm-state-machinename directory.

You can add configuration that is specific to the interactive test driver, by adding to the interactive option. interactive is a copy of the regular test options namespace, and is used by the interactive test driver. It can be helpful for troubleshooting changes that you don’t want to apply to regular test runs.