[v4] Documentation: kunit: Make the KUnit documentation less UML-specific

Commit Message

David Gow Feb. 28, 2020, 7:18 p.m. UTC

Remove some of the outmoded "Why KUnit" rationale, and move some
UML-specific information to the kunit_tool page. Also update the Getting
Started guide to mention running tests without the kunit_tool wrapper.

Signed-off-by: David Gow <[e-mail]>
Reviewed-by: Frank Rowand <[e-mail]>
---
Sorry: I missed a couple of issues in the last version. They're fixed
here, and I think this should be ready to go.

Changelog:

v4:
- Fix typo: s/offsers/offers
- Talk about KUnit tests running on most "architectures" instead of
  "kernel configurations.
v3:
https://lore.kernel.org/linux-kselftest/[e-mail]/T/#u
- Added a note that KUnit can be used with UML, both with and without
  kunit_tool to replace the section moved to kunit_tool.
v2:
https://lore.kernel.org/linux-kselftest/[e-mail]/T/
- Reinstated the "Why Kunit?" section, minus the comparison with other
  testing frameworks (covered in the FAQ), and the description of UML.
- Moved the description of UML into to kunit_tool page.
- Tidied up the wording around how KUnit is built and run to make it
  work
  without the UML description.
v1:
https://lore.kernel.org/linux-kselftest/[e-mail]/T/
- Initial patch

 Documentation/dev-tools/kunit/index.rst      | 40 ++++++----
 Documentation/dev-tools/kunit/kunit-tool.rst |  7 ++
 Documentation/dev-tools/kunit/start.rst      | 80 ++++++++++++++++----
 3 files changed, 99 insertions(+), 28 deletions(-)

Comments

Frank Rowand March 2, 2020, 4:50 p.m. UTC | #1

Hi David,

On 2/28/20 1:18 PM, David Gow wrote:
> Remove some of the outmoded "Why KUnit" rationale, and move some
> UML-specific information to the kunit_tool page. Also update the Getting
> Started guide to mention running tests without the kunit_tool wrapper.
> 
> Signed-off-by: David Gow <[e-mail]>
> Reviewed-by: Frank Rowand <[e-mail]>
> ---
> Sorry: I missed a couple of issues in the last version. They're fixed
> here, and I think this should be ready to go.
> 
> Changelog:
> 
> v4:
> - Fix typo: s/offsers/offers
> - Talk about KUnit tests running on most "architectures" instead of
>   "kernel configurations.
> v3:
> https://lore.kernel.org/linux-kselftest/[e-mail]/T/#u
> - Added a note that KUnit can be used with UML, both with and without
>   kunit_tool to replace the section moved to kunit_tool.
> v2:
> https://lore.kernel.org/linux-kselftest/[e-mail]/T/
> - Reinstated the "Why Kunit?" section, minus the comparison with other
>   testing frameworks (covered in the FAQ), and the description of UML.
> - Moved the description of UML into to kunit_tool page.
> - Tidied up the wording around how KUnit is built and run to make it
>   work
>   without the UML description.
> v1:
> https://lore.kernel.org/linux-kselftest/[e-mail]/T/
> - Initial patch

Thanks for all the changes.  The documents are now much more understandable
and useful.

-Frank

> 
>  Documentation/dev-tools/kunit/index.rst      | 40 ++++++----
>  Documentation/dev-tools/kunit/kunit-tool.rst |  7 ++
>  Documentation/dev-tools/kunit/start.rst      | 80 ++++++++++++++++----
>  3 files changed, 99 insertions(+), 28 deletions(-)
> 
> diff --git a/Documentation/dev-tools/kunit/index.rst b/Documentation/dev-tools/kunit/index.rst
> index d16a4d2c3a41..e93606ecfb01 100644
> --- a/Documentation/dev-tools/kunit/index.rst
> +++ b/Documentation/dev-tools/kunit/index.rst
> @@ -17,14 +17,23 @@ What is KUnit?
>  ==============
>  
>  KUnit is a lightweight unit testing and mocking framework for the Linux kernel.
> -These tests are able to be run locally on a developer's workstation without a VM
> -or special hardware.
>  
>  KUnit is heavily inspired by JUnit, Python's unittest.mock, and
>  Googletest/Googlemock for C++. KUnit provides facilities for defining unit test
>  cases, grouping related test cases into test suites, providing common
>  infrastructure for running tests, and much more.
>  
> +KUnit consists of a kernel component, which provides a set of macros for easily
> +writing unit tests. Tests written against KUnit will run on kernel boot if
> +built-in, or when loaded if built as a module. These tests write out results to
> +the kernel log in `TAP <https://testanything.org/>`_ format.
> +
> +To make running these tests (and reading the results) easier, KUnit offers
> +:doc:`kunit_tool <kunit-tool>`, which builds a `User Mode Linux
> +<http://user-mode-linux.sourceforge.net>`_ kernel, runs it, and parses the test
> +results. This provides a quick way of running KUnit tests during development,
> +without requiring a virtual machine or separate hardware.
> +
>  Get started now: :doc:`start`
>  
>  Why KUnit?
> @@ -36,21 +45,20 @@ allow all possible code paths to be tested in the code under test; this is only
>  possible if the code under test is very small and does not have any external
>  dependencies outside of the test's control like hardware.
>  
> -Outside of KUnit, there are no testing frameworks currently
> -available for the kernel that do not require installing the kernel on a test
> -machine or in a VM and all require tests to be written in userspace running on
> -the kernel; this is true for Autotest, and kselftest, disqualifying
> -any of them from being considered unit testing frameworks.
> +KUnit provides a common framework for unit tests within the kernel.
> +
> +KUnit tests can be run on most architectures, and most tests are architecture
> +independent. All built-in KUnit tests run on kernel startup.  Alternatively,
> +KUnit and KUnit tests can be built as modules and tests will run when the test
> +module is loaded.
>  
> -KUnit addresses the problem of being able to run tests without needing a virtual
> -machine or actual hardware with User Mode Linux. User Mode Linux is a Linux
> -architecture, like ARM or x86; however, unlike other architectures it compiles
> -to a standalone program that can be run like any other program directly inside
> -of a host operating system; to be clear, it does not require any virtualization
> -support; it is just a regular program.
> +.. note::
>  
> -Alternatively, kunit and kunit tests can be built as modules and tests will
> -run when the test module is loaded.
> +        KUnit can also run tests without needing a virtual machine or actual
> +        hardware under User Mode Linux. User Mode Linux is a Linux architecture,
> +        like ARM or x86, which compiles the kernel as a Linux executable. KUnit
> +        can be used with UML either by building with ``ARCH=um`` (like any other
> +        architecture), or by using :doc:`kunit_tool <kunit-tool>`.
>  
>  KUnit is fast. Excluding build time, from invocation to completion KUnit can run
>  several dozen tests in only 10 to 20 seconds; this might not sound like a big
> @@ -81,3 +89,5 @@ How do I use it?
>  *   :doc:`start` - for new users of KUnit
>  *   :doc:`usage` - for a more detailed explanation of KUnit features
>  *   :doc:`api/index` - for the list of KUnit APIs used for testing
> +*   :doc:`kunit-tool` - for more information on the kunit_tool helper script
> +*   :doc:`faq` - for answers to some common questions about KUnit
> diff --git a/Documentation/dev-tools/kunit/kunit-tool.rst b/Documentation/dev-tools/kunit/kunit-tool.rst
> index 50d46394e97e..949af2da81e5 100644
> --- a/Documentation/dev-tools/kunit/kunit-tool.rst
> +++ b/Documentation/dev-tools/kunit/kunit-tool.rst
> @@ -12,6 +12,13 @@ the Linux kernel as UML (`User Mode Linux
>  <http://user-mode-linux.sourceforge.net/>`_), running KUnit tests, parsing
>  the test results and displaying them in a user friendly manner.
>  
> +kunit_tool addresses the problem of being able to run tests without needing a
> +virtual machine or actual hardware with User Mode Linux. User Mode Linux is a
> +Linux architecture, like ARM or x86; however, unlike other architectures it
> +compiles the kernel as a standalone Linux executable that can be run like any
> +other program directly inside of a host operating system. To be clear, it does
> +not require any virtualization support: it is just a regular program.
> +
>  What is a kunitconfig?
>  ======================
>  
> diff --git a/Documentation/dev-tools/kunit/start.rst b/Documentation/dev-tools/kunit/start.rst
> index 4e1d24db6b13..e1c5ce80ce12 100644
> --- a/Documentation/dev-tools/kunit/start.rst
> +++ b/Documentation/dev-tools/kunit/start.rst
> @@ -9,11 +9,10 @@ Installing dependencies
>  KUnit has the same dependencies as the Linux kernel. As long as you can build
>  the kernel, you can run KUnit.
>  
> -KUnit Wrapper
> -=============
> -Included with KUnit is a simple Python wrapper that helps format the output to
> -easily use and read KUnit output. It handles building and running the kernel, as
> -well as formatting the output.
> +Running tests with the KUnit Wrapper
> +====================================
> +Included with KUnit is a simple Python wrapper which runs tests under User Mode
> +Linux, and formats the test results.
>  
>  The wrapper can be run with:
>  
> @@ -21,22 +20,42 @@ The wrapper can be run with:
>  
>  	./tools/testing/kunit/kunit.py run --defconfig
>  
> -For more information on this wrapper (also called kunit_tool) checkout the
> +For more information on this wrapper (also called kunit_tool) check out the
>  :doc:`kunit-tool` page.
>  
>  Creating a .kunitconfig
> -=======================
> -The Python script is a thin wrapper around Kbuild. As such, it needs to be
> -configured with a ``.kunitconfig`` file. This file essentially contains the
> -regular Kernel config, with the specific test targets as well.
> -
> +-----------------------
> +If you want to run a specific set of tests (rather than those listed in the
> +KUnit defconfig), you can provide Kconfig options in the ``.kunitconfig`` file.
> +This file essentially contains the regular Kernel config, with the specific
> +test targets as well. The ``.kunitconfig`` should also contain any other config
> +options required by the tests.
> +
> +A good starting point for a ``.kunitconfig`` is the KUnit defconfig:
>  .. code-block:: bash
>  
>  	cd $PATH_TO_LINUX_REPO
>  	cp arch/um/configs/kunit_defconfig .kunitconfig
>  
> -Verifying KUnit Works
> ----------------------
> +You can then add any other Kconfig options you wish, e.g.:
> +.. code-block:: none
> +
> +        CONFIG_LIST_KUNIT_TEST=y
> +
> +:doc:`kunit_tool <kunit-tool>` will ensure that all config options set in
> +``.kunitconfig`` are set in the kernel ``.config`` before running the tests.
> +It'll warn you if you haven't included the dependencies of the options you're
> +using.
> +
> +.. note::
> +   Note that removing something from the ``.kunitconfig`` will not trigger a
> +   rebuild of the ``.config`` file: the configuration is only updated if the
> +   ``.kunitconfig`` is not a subset of ``.config``. This means that you can use
> +   other tools (such as make menuconfig) to adjust other config options.
> +
> +
> +Running the tests
> +-----------------
>  
>  To make sure that everything is set up correctly, simply invoke the Python
>  wrapper from your kernel repo:
> @@ -62,6 +81,41 @@ followed by a list of tests that are run. All of them should be passing.
>  	Because it is building a lot of sources for the first time, the
>  	``Building KUnit kernel`` step may take a while.
>  
> +Running tests without the KUnit Wrapper
> +=======================================
> +
> +If you'd rather not use the KUnit Wrapper (if, for example, you need to
> +integrate with other systems, or use an architecture other than UML), KUnit can
> +be included in any kernel, and the results read out and parsed manually.
> +
> +.. note::
> +   KUnit is not designed for use in a production system, and it's possible that
> +   tests may reduce the stability or security of the system.
> +
> +
> +
> +Configuring the kernel
> +----------------------
> +
> +In order to enable KUnit itself, you simply need to enable the ``CONFIG_KUNIT``
> +Kconfig option (it's under Kernel Hacking/Kernel Testing and Coverage in
> +menuconfig). From there, you can enable any KUnit tests you want: they usually
> +have config options ending in ``_KUNIT_TEST``.
> +
> +KUnit and KUnit tests can be compiled as modules: in this case the tests in a
> +module will be run when the module is loaded.
> +
> +Running the tests
> +-----------------
> +
> +Build and run your kernel as usual. Test output will be written to the kernel
> +log in `TAP <https://testanything.org/>`_ format.
> +
> +.. note::
> +   It's possible that there will be other lines and/or data interspersed in the
> +   TAP output.
> +
> +
>  Writing your first test
>  =======================
>  
>

shuah March 13, 2020, 4:05 p.m. UTC | #2

On 3/2/20 9:50 AM, Frank Rowand wrote:
> Hi David,
> 
> On 2/28/20 1:18 PM, David Gow wrote:
>> Remove some of the outmoded "Why KUnit" rationale, and move some
>> UML-specific information to the kunit_tool page. Also update the Getting
>> Started guide to mention running tests without the kunit_tool wrapper.
>>
>> Signed-off-by: David Gow <[e-mail]>
>> Reviewed-by: Frank Rowand <[e-mail]>
>> ---
>> Sorry: I missed a couple of issues in the last version. They're fixed
>> here, and I think this should be ready to go.
>>
>> Changelog:
>>
>> v4:
>> - Fix typo: s/offsers/offers
>> - Talk about KUnit tests running on most "architectures" instead of
>>    "kernel configurations.
>> v3:
>> https://lore.kernel.org/linux-kselftest/[e-mail]/T/#u
>> - Added a note that KUnit can be used with UML, both with and without
>>    kunit_tool to replace the section moved to kunit_tool.
>> v2:
>> https://lore.kernel.org/linux-kselftest/[e-mail]/T/
>> - Reinstated the "Why Kunit?" section, minus the comparison with other
>>    testing frameworks (covered in the FAQ), and the description of UML.
>> - Moved the description of UML into to kunit_tool page.
>> - Tidied up the wording around how KUnit is built and run to make it
>>    work
>>    without the UML description.
>> v1:
>> https://lore.kernel.org/linux-kselftest/[e-mail]/T/
>> - Initial patch
> 
> Thanks for all the changes.  The documents are now much more understandable
> and useful.
> 

Is this ready to go? If it goes through doc tree:

Acked-by: Shuah Khan <[e-mail]>

Otherwise, I can pic it up.

thanks,
-- Shuah

Brendan Higgins March 13, 2020, 11:35 p.m. UTC | #3

On Fri, Feb 28, 2020 at 11:18 AM David Gow <[e-mail]> wrote:
>
> Remove some of the outmoded "Why KUnit" rationale, and move some
> UML-specific information to the kunit_tool page. Also update the Getting
> Started guide to mention running tests without the kunit_tool wrapper.
>
> Signed-off-by: David Gow <[e-mail]>
> Reviewed-by: Frank Rowand <[e-mail]>

Reviewed-by: Brendan Higgins <[e-mail]>

Brendan Higgins March 13, 2020, 11:36 p.m. UTC | #4

On Fri, Mar 13, 2020 at 9:05 AM shuah <[e-mail]> wrote:
>
> On 3/2/20 9:50 AM, Frank Rowand wrote:
> > Hi David,
> >
> > On 2/28/20 1:18 PM, David Gow wrote:
> >> Remove some of the outmoded "Why KUnit" rationale, and move some
> >> UML-specific information to the kunit_tool page. Also update the Getting
> >> Started guide to mention running tests without the kunit_tool wrapper.
> >>
> >> Signed-off-by: David Gow <[e-mail]>
> >> Reviewed-by: Frank Rowand <[e-mail]>
> >> ---
> >> Sorry: I missed a couple of issues in the last version. They're fixed
> >> here, and I think this should be ready to go.
> >>
> >> Changelog:
> >>
> >> v4:
> >> - Fix typo: s/offsers/offers
> >> - Talk about KUnit tests running on most "architectures" instead of
> >>    "kernel configurations.
> >> v3:
> >> https://lore.kernel.org/linux-kselftest/[e-mail]/T/#u
> >> - Added a note that KUnit can be used with UML, both with and without
> >>    kunit_tool to replace the section moved to kunit_tool.
> >> v2:
> >> https://lore.kernel.org/linux-kselftest/[e-mail]/T/
> >> - Reinstated the "Why Kunit?" section, minus the comparison with other
> >>    testing frameworks (covered in the FAQ), and the description of UML.
> >> - Moved the description of UML into to kunit_tool page.
> >> - Tidied up the wording around how KUnit is built and run to make it
> >>    work
> >>    without the UML description.
> >> v1:
> >> https://lore.kernel.org/linux-kselftest/[e-mail]/T/
> >> - Initial patch
> >
> > Thanks for all the changes.  The documents are now much more understandable
> > and useful.
> >
>
> Is this ready to go? If it goes through doc tree:
>
> Acked-by: Shuah Khan <[e-mail]>
>
> Otherwise, I can pic it up.

Yep, looks good to me.

Patch

diff --git a/Documentation/dev-tools/kunit/index.rst b/Documentation/dev-tools/kunit/index.rst
index d16a4d2c3a41..e93606ecfb01 100644
--- a/Documentation/dev-tools/kunit/index.rst
+++ b/Documentation/dev-tools/kunit/index.rst
@@ -17,14 +17,23 @@  What is KUnit?
 ==============
 
 KUnit is a lightweight unit testing and mocking framework for the Linux kernel.
-These tests are able to be run locally on a developer's workstation without a VM
-or special hardware.
 
 KUnit is heavily inspired by JUnit, Python's unittest.mock, and
 Googletest/Googlemock for C++. KUnit provides facilities for defining unit test
 cases, grouping related test cases into test suites, providing common
 infrastructure for running tests, and much more.
 
+KUnit consists of a kernel component, which provides a set of macros for easily
+writing unit tests. Tests written against KUnit will run on kernel boot if
+built-in, or when loaded if built as a module. These tests write out results to
+the kernel log in `TAP <https://testanything.org/>`_ format.
+
+To make running these tests (and reading the results) easier, KUnit offers
+:doc:`kunit_tool <kunit-tool>`, which builds a `User Mode Linux
+<http://user-mode-linux.sourceforge.net>`_ kernel, runs it, and parses the test
+results. This provides a quick way of running KUnit tests during development,
+without requiring a virtual machine or separate hardware.
+
 Get started now: :doc:`start`
 
 Why KUnit?
@@ -36,21 +45,20 @@  allow all possible code paths to be tested in the code under test; this is only
 possible if the code under test is very small and does not have any external
 dependencies outside of the test's control like hardware.
 
-Outside of KUnit, there are no testing frameworks currently
-available for the kernel that do not require installing the kernel on a test
-machine or in a VM and all require tests to be written in userspace running on
-the kernel; this is true for Autotest, and kselftest, disqualifying
-any of them from being considered unit testing frameworks.
+KUnit provides a common framework for unit tests within the kernel.
+
+KUnit tests can be run on most architectures, and most tests are architecture
+independent. All built-in KUnit tests run on kernel startup.  Alternatively,
+KUnit and KUnit tests can be built as modules and tests will run when the test
+module is loaded.
 
-KUnit addresses the problem of being able to run tests without needing a virtual
-machine or actual hardware with User Mode Linux. User Mode Linux is a Linux
-architecture, like ARM or x86; however, unlike other architectures it compiles
-to a standalone program that can be run like any other program directly inside
-of a host operating system; to be clear, it does not require any virtualization
-support; it is just a regular program.
+.. note::
 
-Alternatively, kunit and kunit tests can be built as modules and tests will
-run when the test module is loaded.
+        KUnit can also run tests without needing a virtual machine or actual
+        hardware under User Mode Linux. User Mode Linux is a Linux architecture,
+        like ARM or x86, which compiles the kernel as a Linux executable. KUnit
+        can be used with UML either by building with ``ARCH=um`` (like any other
+        architecture), or by using :doc:`kunit_tool <kunit-tool>`.
 
 KUnit is fast. Excluding build time, from invocation to completion KUnit can run
 several dozen tests in only 10 to 20 seconds; this might not sound like a big
@@ -81,3 +89,5 @@  How do I use it?
 *   :doc:`start` - for new users of KUnit
 *   :doc:`usage` - for a more detailed explanation of KUnit features
 *   :doc:`api/index` - for the list of KUnit APIs used for testing
+*   :doc:`kunit-tool` - for more information on the kunit_tool helper script
+*   :doc:`faq` - for answers to some common questions about KUnit
diff --git a/Documentation/dev-tools/kunit/kunit-tool.rst b/Documentation/dev-tools/kunit/kunit-tool.rst
index 50d46394e97e..949af2da81e5 100644
--- a/Documentation/dev-tools/kunit/kunit-tool.rst
+++ b/Documentation/dev-tools/kunit/kunit-tool.rst
@@ -12,6 +12,13 @@  the Linux kernel as UML (`User Mode Linux
 <http://user-mode-linux.sourceforge.net/>`_), running KUnit tests, parsing
 the test results and displaying them in a user friendly manner.
 
+kunit_tool addresses the problem of being able to run tests without needing a
+virtual machine or actual hardware with User Mode Linux. User Mode Linux is a
+Linux architecture, like ARM or x86; however, unlike other architectures it
+compiles the kernel as a standalone Linux executable that can be run like any
+other program directly inside of a host operating system. To be clear, it does
+not require any virtualization support: it is just a regular program.
+
 What is a kunitconfig?
 ======================
 
diff --git a/Documentation/dev-tools/kunit/start.rst b/Documentation/dev-tools/kunit/start.rst
index 4e1d24db6b13..e1c5ce80ce12 100644
--- a/Documentation/dev-tools/kunit/start.rst
+++ b/Documentation/dev-tools/kunit/start.rst
@@ -9,11 +9,10 @@  Installing dependencies
 KUnit has the same dependencies as the Linux kernel. As long as you can build
 the kernel, you can run KUnit.
 
-KUnit Wrapper
-=============
-Included with KUnit is a simple Python wrapper that helps format the output to
-easily use and read KUnit output. It handles building and running the kernel, as
-well as formatting the output.
+Running tests with the KUnit Wrapper
+====================================
+Included with KUnit is a simple Python wrapper which runs tests under User Mode
+Linux, and formats the test results.
 
 The wrapper can be run with:
 
@@ -21,22 +20,42 @@  The wrapper can be run with:
 
 	./tools/testing/kunit/kunit.py run --defconfig
 
-For more information on this wrapper (also called kunit_tool) checkout the
+For more information on this wrapper (also called kunit_tool) check out the
 :doc:`kunit-tool` page.
 
 Creating a .kunitconfig
-=======================
-The Python script is a thin wrapper around Kbuild. As such, it needs to be
-configured with a ``.kunitconfig`` file. This file essentially contains the
-regular Kernel config, with the specific test targets as well.
-
+-----------------------
+If you want to run a specific set of tests (rather than those listed in the
+KUnit defconfig), you can provide Kconfig options in the ``.kunitconfig`` file.
+This file essentially contains the regular Kernel config, with the specific
+test targets as well. The ``.kunitconfig`` should also contain any other config
+options required by the tests.
+
+A good starting point for a ``.kunitconfig`` is the KUnit defconfig:
 .. code-block:: bash
 
 	cd $PATH_TO_LINUX_REPO
 	cp arch/um/configs/kunit_defconfig .kunitconfig
 
-Verifying KUnit Works
----------------------
+You can then add any other Kconfig options you wish, e.g.:
+.. code-block:: none
+
+        CONFIG_LIST_KUNIT_TEST=y
+
+:doc:`kunit_tool <kunit-tool>` will ensure that all config options set in
+``.kunitconfig`` are set in the kernel ``.config`` before running the tests.
+It'll warn you if you haven't included the dependencies of the options you're
+using.
+
+.. note::
+   Note that removing something from the ``.kunitconfig`` will not trigger a
+   rebuild of the ``.config`` file: the configuration is only updated if the
+   ``.kunitconfig`` is not a subset of ``.config``. This means that you can use
+   other tools (such as make menuconfig) to adjust other config options.
+
+
+Running the tests
+-----------------
 
 To make sure that everything is set up correctly, simply invoke the Python
 wrapper from your kernel repo:
@@ -62,6 +81,41 @@  followed by a list of tests that are run. All of them should be passing.
 	Because it is building a lot of sources for the first time, the
 	``Building KUnit kernel`` step may take a while.
 
+Running tests without the KUnit Wrapper
+=======================================
+
+If you'd rather not use the KUnit Wrapper (if, for example, you need to
+integrate with other systems, or use an architecture other than UML), KUnit can
+be included in any kernel, and the results read out and parsed manually.
+
+.. note::
+   KUnit is not designed for use in a production system, and it's possible that
+   tests may reduce the stability or security of the system.
+
+
+
+Configuring the kernel
+----------------------
+
+In order to enable KUnit itself, you simply need to enable the ``CONFIG_KUNIT``
+Kconfig option (it's under Kernel Hacking/Kernel Testing and Coverage in
+menuconfig). From there, you can enable any KUnit tests you want: they usually
+have config options ending in ``_KUNIT_TEST``.
+
+KUnit and KUnit tests can be compiled as modules: in this case the tests in a
+module will be run when the module is loaded.
+
+Running the tests
+-----------------
+
+Build and run your kernel as usual. Test output will be written to the kernel
+log in `TAP <https://testanything.org/>`_ format.
+
+.. note::
+   It's possible that there will be other lines and/or data interspersed in the
+   TAP output.
+
+
 Writing your first test
 =======================