Hello Tim, Thanks for your comments. See my comments below. On Tue, Dec 7, 2021 at 10:41 PM <Tim.Bird@xxxxxxxx> wrote: > > 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 > Done > > > + > > +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 > Regards, Harinder Singh
