# Running Tests interactively

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).

## Reuse VM state

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.

## Interactive-only test configuration

The `.driverInteractive` attribute combines the regular test configuration with definitions from the `interactive` submodule. This gives you a more usable, graphical, but slightly different configuration.

You can add your own interactive-only test configuration by adding extra configuration to the `interactive` submodule.

To interactively run only the regular configuration, build the `<test>.driver` attribute instead, and call it with the flag `result/bin/nixos-test-driver --interactive`.