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The "How Do I Use This" section of index.rst and "Next Steps" section of
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(which already had the TOC visible) or when reading the source (where
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Instead, provide a small number of concrete next steps, and a bit more
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This also removes the broken reference to 'tips.rst', which was
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Fixed git am whitespace complaints during commit:
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Fixes: 4399c737a97d ("Documentation: kunit: Remove redundant 'tips.rst' page")
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Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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.. SPDX-License-Identifier: GPL-2.0
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=================================
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KUnit - Linux Kernel Unit Testing
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=================================
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.. toctree::
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:maxdepth: 2
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:caption: Contents:
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start
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architecture
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run_wrapper
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run_manual
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usage
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api/index
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style
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faq
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running_tips
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This section details the kernel unit testing framework.
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Introduction
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============
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KUnit (Kernel unit testing framework) provides a common framework for
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unit tests within the Linux kernel. Using KUnit, you can define groups
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of test cases called test suites. The tests either run on kernel boot
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if built-in, or load as a module. KUnit automatically flags and reports
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failed test cases in the kernel log. The test results appear in
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:doc:`KTAP (Kernel - Test Anything Protocol) format</dev-tools/ktap>`.
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It is inspired by JUnit, Python’s unittest.mock, and GoogleTest/GoogleMock
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(C++ unit testing framework).
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KUnit tests are part of the kernel, written in the C (programming)
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language, and test parts of the Kernel implementation (example: a C
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language function). Excluding build time, from invocation to
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completion, KUnit can run around 100 tests in less than 10 seconds.
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KUnit can test any kernel component, for example: file system, system
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calls, memory management, device drivers and so on.
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KUnit follows the white-box testing approach. The test has access to
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internal system functionality. KUnit runs in kernel space and is not
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restricted to things exposed to user-space.
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In addition, KUnit has kunit_tool, a script (``tools/testing/kunit/kunit.py``)
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that configures the Linux kernel, runs KUnit tests under QEMU or UML
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(:doc:`User Mode Linux </virt/uml/user_mode_linux_howto_v2>`),
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parses the test results and
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displays them in a user friendly manner.
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Features
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--------
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- Provides a framework for writing unit tests.
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- Runs tests on any kernel architecture.
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- Runs a test in milliseconds.
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Prerequisites
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-------------
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- Any Linux kernel compatible hardware.
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- For Kernel under test, Linux kernel version 5.5 or greater.
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Unit Testing
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============
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A unit test tests a single unit of code in isolation. A unit test is the finest
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granularity of testing and allows all possible code paths to be tested in the
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code under test. This is possible if the code under test is small and does not
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have any external dependencies outside of the test's control like hardware.
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Write Unit Tests
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----------------
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To write good unit tests, there is a simple but powerful pattern:
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Arrange-Act-Assert. This is a great way to structure test cases and
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defines an order of operations.
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- Arrange inputs and targets: At the start of the test, arrange the data
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that allows a function to work. Example: initialize a statement or
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object.
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- Act on the target behavior: Call your function/code under test.
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- Assert expected outcome: Verify that the result (or resulting state) is as
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expected.
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Unit Testing Advantages
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-----------------------
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- Increases testing speed and development in the long run.
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- Detects bugs at initial stage and therefore decreases bug fix cost
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compared to acceptance testing.
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- Improves code quality.
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- Encourages writing testable code.
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Read also :ref:`kinds-of-tests`.
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How do I use it?
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================
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You can find a step-by-step guide to writing and running KUnit tests in
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Documentation/dev-tools/kunit/start.rst
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Alternatively, feel free to look through the rest of the KUnit documentation,
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or to experiment with tools/testing/kunit/kunit.py and the example test under
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lib/kunit/kunit-example-test.c
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Happy testing!
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