===========
Using KUnit
===========

.. toctree::
   :maxdepth: 2
   :caption: Contents:

   getting_kunit
   faq

Where is KUnit?
:doc:`getting_kunit`


KUnit is integrated into the Linux kernel, so all you need is a version of the
kernel which contains KUnit, and a config file with which to build it. The
:doc:`getting_kunit` page covers the different versions of KUnit available, and
where to get them.


Running tests
=============

To run KUnit tests, you'll need to provide a 'kunitconfig' file, which contains
the list of test modules to build, and their dependencies.

Once you have the ``kunitconfig`` file, just run:

.. code-block:: bash

   ./tools/testing/kunit/kunit.py run

.. tip::

   You may want to run KUnit with flags like:

   .. code-block:: bash

      ./tools/testing/kunit/kunit.py run --timeout=30 --jobs=24 --defconfig

   - ``--timeout`` sets a maximum amount of time to allow tests to run.
   - ``--jobs`` sets the number of threads to use to build the kernel.
   - ``--defconfig`` uses an default kunitconfig in the kernel source.

   For more information on these and other flags, try running:

   .. code-block:: bash

      ./tools/testing/kunit/kunit.py run --help

This will build a UML (User Mode Linux) kernel, run the specified tests, and
print the results (nicely formatted) to the screen.

.. tip::

   If you get the error message: ``/bin/sh: flex: command not found`` or
   similarly ``/bin/sh: bison: command not found``, you are most likely missing
   the flex and bison packages. On a system using the apt package manager you
   can install them with

   .. code-block:: bash

      sudo apt-get install flex bison

   For more information on building the kernel, see
   https://www.kernel.org/doc/html/latest/process/changes.html

Writing tests
=============

Once you have KUnit working, writing tests is easy. Each test is a function
which accepts a ``struct kunit`` argument, and which calls the various
``KUNIT_EXPECT_*`` macros to verify the state under test.

More details can be found in the `Getting Started <../third_party/kernel/docs/start.html>`_
guide.


Submitting tests upstream
=========================

Ideally, KUnit tests will be submitted upstream alongside the code being tested,
so any user or developer can run the tests and test any changes they make.
Unless they affect KUnit itself, this means that KUnit tests should ideally be
treated as any other change, and submitted via the maintainer of the subsystem
being tested. (Though do feel free to copy in the
``kunit-dev@googlegroups.com`` list if you want.)

For changes to KUnit itself, we recommend submitting patches via the
``linux-kselftest/kunit`` branch, which contains the version of KUnit likely to
head upstream. To do so, please send your patch via the
``linux-kselftest@vger.kernel.org`` list. You should still get a review from
any relevant the subsystem maintainers, though.

And, of course, you should follow the general rules and guidelines laid out in
https://www.kernel.org/doc/html/latest/process/submitting-patches.html