<section xmlns="http://docbook.org/ns/docbook"
        xmlns:xlink="http://www.w3.org/1999/xlink"
        xmlns:xi="http://www.w3.org/2001/XInclude"
        version="5.0"
        xml:id="sec-running-nixos-tests">
<title>Running Tests interactively</title>

<para>The test itself can be run interactively.  This is
particularly useful when developing or debugging a test:

<screen>
$ nix-build nixos/tests/login.nix -A driver
$ ./result/bin/nixos-test-driver
starting VDE switch for network 1
&gt;
</screen>

You can then take any Perl statement, e.g.

<screen>
&gt; startAll
&gt; testScript
&gt; $machine->succeed("touch /tmp/foo")
</screen>

The function <command>testScript</command> 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).</para>

<para>To just start and experiment with the VMs, run:

<screen>
$ nix-build nixos/tests/login.nix -A driver
$ ./result/bin/nixos-run-vms
</screen>

The script <command>nixos-run-vms</command> 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
<filename>./</filename><varname>hostname</varname><filename>.qcow2</filename>.</para>

</section>
