https://github.com/torvalds/linux
Tip revision: 26291c54e111ff6ba87a164d85d4a4e134b7315c authored by Linus Torvalds on 30 January 2022, 13:37:07 UTC
Linux 5.17-rc2
Linux 5.17-rc2
Tip revision: 26291c5
start.rst
.. SPDX-License-Identifier: GPL-2.0
===============
Getting Started
===============
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
For more information on this wrapper, see:
Documentation/dev-tools/kunit/run_wrapper.rst.
Creating a ``.kunitconfig``
---------------------------
By default, kunit_tool runs a selection of tests. However, you can specify which
unit tests to run by creating a ``.kunitconfig`` file with kernel config options
that enable only a specific set of tests and their dependencies.
The ``.kunitconfig`` file contains a list of kconfig options which are required
to run the desired targets. The ``.kunitconfig`` also contains any other test
specific config options, such as test dependencies. For example: the
``FAT_FS`` tests - ``FAT_KUNIT_TEST``, depends on
``FAT_FS``. ``FAT_FS`` can be enabled by selecting either ``MSDOS_FS``
or ``VFAT_FS``. To run ``FAT_KUNIT_TEST``, the ``.kunitconfig`` has:
.. code-block:: none
CONFIG_KUNIT=y
CONFIG_MSDOS_FS=y
CONFIG_FAT_KUNIT_TEST=y
1. A good starting point for the ``.kunitconfig``, is the KUnit default
config. Run the command:
.. code-block:: bash
cd $PATH_TO_LINUX_REPO
cp tools/testing/kunit/configs/default.config .kunitconfig
.. note ::
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.
2. You can then add any other Kconfig options, for example:
.. code-block:: none
CONFIG_LIST_KUNIT_TEST=y
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.
.. note ::
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.
Running Tests (KUnit Wrapper)
-----------------------------
1. To make sure that everything is set up correctly, invoke the Python
wrapper from your kernel repository:
.. code-block:: bash
./tools/testing/kunit/kunit.py run
If everything worked correctly, you should see the following:
.. code-block::
Generating .config ...
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`` may take a while.
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);
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=y
default KUNIT_ALL_TESTS
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 ``.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
==========
* Documentation/dev-tools/kunit/architecture.rst - KUnit architecture.
* Documentation/dev-tools/kunit/run_wrapper.rst - run kunit_tool.
* Documentation/dev-tools/kunit/run_manual.rst - run tests without kunit_tool.
* Documentation/dev-tools/kunit/usage.rst - write tests.
* Documentation/dev-tools/kunit/tips.rst - best practices with
examples.
* Documentation/dev-tools/kunit/api/index.rst - KUnit APIs
used for testing.
* Documentation/dev-tools/kunit/kunit-tool.rst - kunit_tool helper
script.
* Documentation/dev-tools/kunit/faq.rst - KUnit common questions and
answers.