See one additional suggestion below. -- Tim > -----Original Message----- > From: Harinder Singh <sharinder@xxxxxxxxxx> > > Add a section on advantages of unit testing, how to write unit tests, > KUnit features and Prerequisites. > > Signed-off-by: Harinder Singh <sharinder@xxxxxxxxxx> > --- > Documentation/dev-tools/kunit/index.rst | 166 +++++++++++++----------- > 1 file changed, 88 insertions(+), 78 deletions(-) > > diff --git a/Documentation/dev-tools/kunit/index.rst b/Documentation/dev-tools/kunit/index.rst > index cacb35ec658d..ebf4bffaa1ca 100644 > --- a/Documentation/dev-tools/kunit/index.rst > +++ b/Documentation/dev-tools/kunit/index.rst > @@ -1,11 +1,12 @@ > .. SPDX-License-Identifier: GPL-2.0 > > -========================================= > -KUnit - Unit Testing for the Linux Kernel > -========================================= > +================================= > +KUnit - Linux Kernel Unit Testing > +================================= > > .. toctree:: > :maxdepth: 2 > + :caption: Contents: > > start > usage > @@ -16,82 +17,91 @@ KUnit - Unit Testing for the Linux Kernel > tips > running_tips > > -What is KUnit? > -============== > - > -KUnit is a lightweight unit testing and mocking framework for the Linux kernel. > - > -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: Documentation/dev-tools/kunit/start.rst > - > -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. > - > -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. > - > -.. note:: > - > - 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 > -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? > +This section details the kernel unit testing framework. > + > +Introduction > +============ > + > +KUnit (Kernel unit testing framework) provides a common framework for > +unit tests within the Linux kernel. Using KUnit, you can define groups > +of test cases called test suites. The tests either run on kernel boot > +if built-in, or load as a module. KUnit automatically flags and reports > +failed test cases in the kernel log. The test results appear in `TAP > +(Test Anything Protocol) format <https://testanything.org/>`_. It is inspired by > +JUnit, Python’s unittest.mock, and GoogleTest/GoogleMock (C++ unit testing > +framework). > + > +KUnit tests are part of the kernel, written in the C (programming) > +language, and test parts of the Kernel implementation (example: a C > +language function). Excluding build time, from invocation to > +completion, KUnit can run around 100 tests in less than 10 seconds. > +KUnit can test any kernel component, for example: file system, system > +calls, memory management, device drivers and so on. > + > +KUnit follows the white-box testing approach. The test has access to > +internal system functionality. KUnit runs in kernel space and is not > +restricted to things exposed to user-space. > + > +In addition, KUnit has kunit_tool, a script (``tools/testing/kunit/kunit.py``) > +that configures the Linux kernel, runs KUnit tests under QEMU or UML (`User Mode > +Linux <http://user-mode-linux.sourceforge.net/>`_), parses the test results and > +displays them in a user friendly manner. > + > +Features > +-------- > + > +- Provides a framework for writing unit tests. > +- Runs tests on any kernel architecture. > +- Runs a test in milliseconds. > + > +Prerequisites > +------------- > + > +- Any Linux kernel compatible hardware. > +- For Kernel under test, Linux kernel version 5.5 or greater. > + > +Unit Testing > +============ > + > +A unit test tests a single unit of code in isolation. A unit test is the finest > +granularity of testing and allows all possible code paths to be tested in the > +code under test. This is possible if the code under test is small and does not > +have any external dependencies outside of the test's control like hardware. > + > + > +Write Unit Tests > +---------------- > + > +To write good unit tests, there is a simple but powerful pattern: > +Arrange-Act-Assert. This is a great way to structure test cases and > +defines an order of operations. > + > +- Arrange inputs and targets: At the start of the test, arrange the data > + that allows a function to work. Example: initialize a statement or > + object. > +- Act on the target behavior: Call your function/code under test. > +- Assert expected outcome: Verify the result (or resulting state) as expected > + or not. Verify the result (or resulting state) as expected or not -> Verify that the result (or resulting state) is as expected or not > + > +Unit Testing Advantages > +----------------------- > + > +- Increases testing speed and development in the long run. > +- Detects bugs at initial stage and therefore decreases bug fix cost > + compared to acceptance testing. > +- Improves code quality. > +- Encourages writing testable code. > > How do I use it? > ================ > > -* Documentation/dev-tools/kunit/start.rst - for new users of KUnit > -* Documentation/dev-tools/kunit/tips.rst - for short examples of best practices > -* Documentation/dev-tools/kunit/usage.rst - for a more detailed explanation of KUnit features > -* Documentation/dev-tools/kunit/api/index.rst - for the list of KUnit APIs used for testing > -* Documentation/dev-tools/kunit/kunit-tool.rst - for more information on the kunit_tool helper script > -* Documentation/dev-tools/kunit/faq.rst - for answers to some common questions about KUnit > +* Documentation/dev-tools/kunit/start.rst - for KUnit new users. > +* Documentation/dev-tools/kunit/usage.rst - KUnit features. > +* 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. > -- > 2.34.1.400.ga245620fadb-goog
