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nixpkgs/nixos/doc/manual/development/running-nixos-tests-interactively.xml
Félix Baylac-Jacqué 7e7aa529d9
test-driver.py: delete VM state directory after test run
Keeping the VM state test across several run sometimes lead to subtle
and hard to spot errors in practice. We delete the VM state which
contains (among other things) the qcow volume.

We also introduce a -K (--keep-vm-state) flag making VM state to
persist after the test run. This flag makes test-driver.py to match
its previous behaviour.
2020-06-21 10:27:51 +02:00

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XML

<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-interactively">
<title>Running Tests interactively</title>
<para>
The test itself can be run interactively. This is particularly useful when
developing or debugging a test:
<screen>
<prompt>$ </prompt>nix-build nixos/tests/login.nix -A driver
<prompt>$ </prompt>./result/bin/nixos-test-driver
starting VDE switch for network 1
<prompt>&gt;</prompt>
</screen>
You can then take any Python statement, e.g.
<screen>
<prompt>&gt;</prompt> start_all()
<prompt>&gt;</prompt> test_script()
<prompt>&gt;</prompt> machine.succeed("touch /tmp/foo")
<prompt>&gt;</prompt> print(machine.succeed("pwd")) # Show stdout of command
</screen>
The function <command>test_script</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>
<prompt>$ </prompt>nix-build nixos/tests/login.nix -A driver
<prompt>$ </prompt>./result/bin/nixos-run-vms
</screen>
The script <command>nixos-run-vms</command> starts the virtual machines
defined by test.
</para>
<para>
You can re-use the VM states coming from a previous run
by setting the <command>--keep-vm-state</command> flag.
<screen>
<prompt>$ </prompt>./result/bin/nixos-run-vms --keep-vm-state
</screen>
The machine state is stored in the
<filename>$TMPDIR/vm-state-</filename><varname>machinename</varname> directory.
</para>
</section>