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+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Getting Started
+===============
+
+This page contains an overview of the kunit_tool and KUnit framework,
+teaching how to run existing tests and then how to write a simple test case,
+and covers common problems users face when using KUnit for the first time.
+
+Installing Dependencies
+=======================
+KUnit has the same dependencies as the Linux kernel. As long as you can
+build the kernel, you can run KUnit.
+
+Running tests with kunit_tool
+=============================
+kunit_tool is a Python script, which configures and builds a kernel, runs
+tests, and formats the test results. From the kernel repository, you
+can run kunit_tool:
+
+.. code-block:: bash
+
+ ./tools/testing/kunit/kunit.py run
+
+.. note ::
+ You may see the following error:
+ "The source tree is not clean, please run 'make ARCH=um mrproper'"
+
+ This happens because internally kunit.py specifies ``.kunit``
+ (default option) as the build directory in the command ``make O=output/dir``
+ through the argument ``--build_dir``. Hence, before starting an
+ out-of-tree build, the source tree must be clean.
+
+ There is also the same caveat mentioned in the "Build directory for
+ the kernel" section of the :doc:`admin-guide </admin-guide/README>`,
+ that is, its use, it must be used for all invocations of ``make``.
+ The good news is that it can indeed be solved by running
+ ``make ARCH=um mrproper``, just be aware that this will delete the
+ current configuration and all generated files.
+
+If everything worked correctly, you should see the following:
+
+.. code-block::
+
+ Configuring KUnit Kernel ...
+ Building KUnit Kernel ...
+ Starting KUnit Kernel ...
+
+The tests will pass or fail.
+
+.. note ::
+ Because it is building a lot of sources for the first time,
+ the ``Building KUnit Kernel`` step may take a while.
+
+For detailed information on this wrapper, see:
+Documentation/dev-tools/kunit/run_wrapper.rst.
+
+Selecting which tests to run
+----------------------------
+
+By default, kunit_tool runs all tests reachable with minimal configuration,
+that is, using default values for most of the kconfig options. However,
+you can select which tests to run by:
+
+- `Customizing Kconfig`_ used to compile the kernel, or
+- `Filtering tests by name`_ to select specifically which compiled tests to run.
+
+Customizing Kconfig
+~~~~~~~~~~~~~~~~~~~
+A good starting point for the ``.kunitconfig`` is the KUnit default config.
+If you didn't run ``kunit.py run`` yet, you can generate it by running:
+
+.. code-block:: bash
+
+ cd $PATH_TO_LINUX_REPO
+ tools/testing/kunit/kunit.py config
+ cat .kunit/.kunitconfig
+
+.. note ::
+ ``.kunitconfig`` lives in the ``--build_dir`` used by kunit.py, which is
+ ``.kunit`` by default.
+
+Before running the tests, kunit_tool ensures that all config options
+set in ``.kunitconfig`` are set in the kernel ``.config``. It will warn
+you if you have not included dependencies for the options used.
+
+There are many ways to customize the configurations:
+
+a. Edit ``.kunit/.kunitconfig``. The file should contain the list of kconfig
+ options required to run the desired tests, including their dependencies.
+ You may want to remove CONFIG_KUNIT_ALL_TESTS from the ``.kunitconfig`` as
+ it will enable a number of additional tests that you may not want.
+ If you need to run on an architecture other than UML see :ref:`kunit-on-qemu`.
+
+b. Enable additional kconfig options on top of ``.kunit/.kunitconfig``.
+ For example, to include the kernel's linked-list test you can run::
+
+ ./tools/testing/kunit/kunit.py run \
+ --kconfig_add CONFIG_LIST_KUNIT_TEST=y
+
+c. Provide the path of one or more .kunitconfig files from the tree.
+ For example, to run only ``FAT_FS`` and ``EXT4`` tests you can run::
+
+ ./tools/testing/kunit/kunit.py run \
+ --kunitconfig ./fs/fat/.kunitconfig \
+ --kunitconfig ./fs/ext4/.kunitconfig
+
+d. If you change the ``.kunitconfig``, kunit.py will trigger a rebuild of the
+ ``.config`` file. But you can edit the ``.config`` file directly or with
+ tools like ``make menuconfig O=.kunit``. As long as its a superset of
+ ``.kunitconfig``, kunit.py won't overwrite your changes.
+
+
+.. note ::
+
+ To save a .kunitconfig after finding a satisfactory configuration::
+
+ make savedefconfig O=.kunit
+ cp .kunit/defconfig .kunit/.kunitconfig
+
+Filtering tests by name
+~~~~~~~~~~~~~~~~~~~~~~~
+If you want to be more specific than Kconfig can provide, it is also possible
+to select which tests to execute at boot-time by passing a glob filter
+(read instructions regarding the pattern in the manpage :manpage:`glob(7)`).
+If there is a ``"."`` (period) in the filter, it will be interpreted as a
+separator between the name of the test suite and the test case,
+otherwise, it will be interpreted as the name of the test suite.
+For example, let's assume we are using the default config:
+
+a. inform the name of a test suite, like ``"kunit_executor_test"``,
+ to run every test case it contains::
+
+ ./tools/testing/kunit/kunit.py run "kunit_executor_test"
+
+b. inform the name of a test case prefixed by its test suite,
+ like ``"example.example_simple_test"``, to run specifically that test case::
+
+ ./tools/testing/kunit/kunit.py run "example.example_simple_test"
+
+c. use wildcard characters (``*?[``) to run any test case that matches the pattern,
+ like ``"*.*64*"`` to run test cases containing ``"64"`` in the name inside
+ any test suite::
+
+ ./tools/testing/kunit/kunit.py run "*.*64*"
+
+Running Tests without the KUnit Wrapper
+=======================================
+If you do not want to use the KUnit Wrapper (for example: you want code
+under test to integrate with other systems, or use a different/
+unsupported architecture or configuration), KUnit can be included in
+any kernel, and the results are read out and parsed manually.
+
+.. note ::
+ ``CONFIG_KUNIT`` should not be enabled in a production environment.
+ Enabling KUnit disables Kernel Address-Space Layout Randomization
+ (KASLR), and tests may affect the state of the kernel in ways not
+ suitable for production.
+
+Configuring the Kernel
+----------------------
+To enable KUnit itself, you need to enable the ``CONFIG_KUNIT`` Kconfig
+option (under Kernel Hacking/Kernel Testing and Coverage in
+``menuconfig``). From there, you can enable any KUnit tests. They
+usually have config options ending in ``_KUNIT_TEST``.
+
+KUnit and KUnit tests can be compiled as modules. The tests in a module
+will run when the module is loaded.
+
+Running Tests (without KUnit Wrapper)
+-------------------------------------
+Build and run your kernel. In the kernel log, the test output is printed
+out in the TAP format. This will only happen by default if KUnit/tests
+are built-in. Otherwise the module will need to be loaded.
+
+.. note ::
+ Some lines and/or data may get interspersed in the TAP output.
+
+Writing Your First Test
+=======================
+In your kernel repository, let's add some code that we can test.
+
+1. Create a file ``drivers/misc/example.h``, which includes:
+
+.. code-block:: c
+
+ int misc_example_add(int left, int right);
+
+2. Create a file ``drivers/misc/example.c``, which includes:
+
+.. code-block:: c
+
+ #include <linux/errno.h>
+
+ #include "example.h"
+
+ int misc_example_add(int left, int right)
+ {
+ return left + right;
+ }
+
+3. Add the following lines to ``drivers/misc/Kconfig``:
+
+.. code-block:: kconfig
+
+ config MISC_EXAMPLE
+ bool "My example"
+
+4. Add the following lines to ``drivers/misc/Makefile``:
+
+.. code-block:: make
+
+ obj-$(CONFIG_MISC_EXAMPLE) += example.o
+
+Now we are ready to write the test cases.
+
+1. Add the below test case in ``drivers/misc/example_test.c``:
+
+.. code-block:: c
+
+ #include <kunit/test.h>
+ #include "example.h"
+
+ /* Define the test cases. */
+
+ static void misc_example_add_test_basic(struct kunit *test)
+ {
+ KUNIT_EXPECT_EQ(test, 1, misc_example_add(1, 0));
+ KUNIT_EXPECT_EQ(test, 2, misc_example_add(1, 1));
+ KUNIT_EXPECT_EQ(test, 0, misc_example_add(-1, 1));
+ KUNIT_EXPECT_EQ(test, INT_MAX, misc_example_add(0, INT_MAX));
+ KUNIT_EXPECT_EQ(test, -1, misc_example_add(INT_MAX, INT_MIN));
+ }
+
+ static void misc_example_test_failure(struct kunit *test)
+ {
+ KUNIT_FAIL(test, "This test never passes.");
+ }
+
+ static struct kunit_case misc_example_test_cases[] = {
+ KUNIT_CASE(misc_example_add_test_basic),
+ KUNIT_CASE(misc_example_test_failure),
+ {}
+ };
+
+ static struct kunit_suite misc_example_test_suite = {
+ .name = "misc-example",
+ .test_cases = misc_example_test_cases,
+ };
+ kunit_test_suite(misc_example_test_suite);
+
+ MODULE_LICENSE("GPL");
+
+2. Add the following lines to ``drivers/misc/Kconfig``:
+
+.. code-block:: kconfig
+
+ config MISC_EXAMPLE_TEST
+ tristate "Test for my example" if !KUNIT_ALL_TESTS
+ depends on MISC_EXAMPLE && KUNIT
+ default KUNIT_ALL_TESTS
+
+Note: If your test does not support being built as a loadable module (which is
+discouraged), replace tristate by bool, and depend on KUNIT=y instead of KUNIT.
+
+3. Add the following lines to ``drivers/misc/Makefile``:
+
+.. code-block:: make
+
+ obj-$(CONFIG_MISC_EXAMPLE_TEST) += example_test.o
+
+4. Add the following lines to ``.kunit/.kunitconfig``:
+
+.. code-block:: none
+
+ CONFIG_MISC_EXAMPLE=y
+ CONFIG_MISC_EXAMPLE_TEST=y
+
+5. Run the test:
+
+.. code-block:: bash
+
+ ./tools/testing/kunit/kunit.py run
+
+You should see the following failure:
+
+.. code-block:: none
+
+ ...
+ [16:08:57] [PASSED] misc-example:misc_example_add_test_basic
+ [16:08:57] [FAILED] misc-example:misc_example_test_failure
+ [16:08:57] EXPECTATION FAILED at drivers/misc/example-test.c:17
+ [16:08:57] This test never passes.
+ ...
+
+Congrats! You just wrote your first KUnit test.
+
+Next Steps
+==========
+
+If you're interested in using some of the more advanced features of kunit.py,
+take a look at Documentation/dev-tools/kunit/run_wrapper.rst
+
+If you'd like to run tests without using kunit.py, check out
+Documentation/dev-tools/kunit/run_manual.rst
+
+For more information on writing KUnit tests (including some common techniques
+for testing different things), see Documentation/dev-tools/kunit/usage.rst