Remove some of the outmoded "Why KUnit" rationale -- which focuses significantly on UML -- and update the Getting Started guide to mention running tests without the kunit_tool wrapper. Signed-off-by: David Gow <davidgow@xxxxxxxxxx> --- This is an attempt at resolving some of the issues with the KUnit documentation pointed out here: https://lore.kernel.org/linux-kselftest/CABVgOSkiLi0UNijH1xTSvmsJEE5+ocCZ7nkzmKzxDLzzfqBSzQ@xxxxxxxxxxxxxx/ There's definitely room for further work on the KUnit documentation (e.g., adding more information around the environment tests run in), but this hopefully is better than nothing as a starting point. Documentation/dev-tools/kunit/index.rst | 60 ++++--------------- Documentation/dev-tools/kunit/start.rst | 80 +++++++++++++++++++++---- 2 files changed, 78 insertions(+), 62 deletions(-) diff --git a/Documentation/dev-tools/kunit/index.rst b/Documentation/dev-tools/kunit/index.rst index d16a4d2c3a41..6064cd14dfad 100644 --- a/Documentation/dev-tools/kunit/index.rst +++ b/Documentation/dev-tools/kunit/index.rst @@ -17,63 +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. -Get started now: :doc:`start` - -Why KUnit? -========== - -A unit test is supposed to test a single unit of code in isolation, hence the -name. A unit test should be the finest granularity of testing and as such should -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 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. -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. +To make running these tests (and reading the results) easier, KUnit offsers +: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. -Alternatively, kunit and kunit tests can be built as modules and tests will -run when the test module is loaded. - -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 -deal to some people, but having such fast and easy to run tests fundamentally -changes the way you go about testing and even writing code in the first place. -Linus himself said in his `git talk at Google -<https://gist.github.com/lorn/1272686/revisions#diff-53c65572127855f1b003db4064a94573R874>`_: - - "... a lot of people seem to think that performance is about doing the - same thing, just doing it faster, and that is not true. That is not what - performance is all about. If you can do something really fast, really - well, people will start using it differently." - -In this context Linus was talking about branching and merging, -but this point also applies to testing. If your tests are slow, unreliable, are -difficult to write, and require a special setup or special hardware to run, -then you wait a lot longer to write tests, and you wait a lot longer to run -tests; this means that tests are likely to break, unlikely to test a lot of -things, and are unlikely to be rerun once they pass. If your tests are really -fast, you run them all the time, every time you make a change, and every time -someone sends you some code. Why trust that someone ran all their tests -correctly on every change when you can just run them yourself in less time than -it takes to read their test log? +Get started now: :doc:`start` How do I use it? ================ @@ -81,3 +41,5 @@ 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/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 ======================= -- 2.25.0.341.g760bfbb309-goog
