index.rst (3863B)
1.. SPDX-License-Identifier: GPL-2.0 2 3================================= 4KUnit - Linux Kernel Unit Testing 5================================= 6 7.. toctree:: 8 :maxdepth: 2 9 :caption: Contents: 10 11 start 12 architecture 13 run_wrapper 14 run_manual 15 usage 16 kunit-tool 17 api/index 18 style 19 faq 20 tips 21 running_tips 22 23This section details the kernel unit testing framework. 24 25Introduction 26============ 27 28KUnit (Kernel unit testing framework) provides a common framework for 29unit tests within the Linux kernel. Using KUnit, you can define groups 30of test cases called test suites. The tests either run on kernel boot 31if built-in, or load as a module. KUnit automatically flags and reports 32failed test cases in the kernel log. The test results appear in `TAP 33(Test Anything Protocol) format <https://testanything.org/>`_. It is inspired by 34JUnit, Python’s unittest.mock, and GoogleTest/GoogleMock (C++ unit testing 35framework). 36 37KUnit tests are part of the kernel, written in the C (programming) 38language, and test parts of the Kernel implementation (example: a C 39language function). Excluding build time, from invocation to 40completion, KUnit can run around 100 tests in less than 10 seconds. 41KUnit can test any kernel component, for example: file system, system 42calls, memory management, device drivers and so on. 43 44KUnit follows the white-box testing approach. The test has access to 45internal system functionality. KUnit runs in kernel space and is not 46restricted to things exposed to user-space. 47 48In addition, KUnit has kunit_tool, a script (``tools/testing/kunit/kunit.py``) 49that configures the Linux kernel, runs KUnit tests under QEMU or UML (`User Mode 50Linux <http://user-mode-linux.sourceforge.net/>`_), parses the test results and 51displays them in a user friendly manner. 52 53Features 54-------- 55 56- Provides a framework for writing unit tests. 57- Runs tests on any kernel architecture. 58- Runs a test in milliseconds. 59 60Prerequisites 61------------- 62 63- Any Linux kernel compatible hardware. 64- For Kernel under test, Linux kernel version 5.5 or greater. 65 66Unit Testing 67============ 68 69A unit test tests a single unit of code in isolation. A unit test is the finest 70granularity of testing and allows all possible code paths to be tested in the 71code under test. This is possible if the code under test is small and does not 72have any external dependencies outside of the test's control like hardware. 73 74 75Write Unit Tests 76---------------- 77 78To write good unit tests, there is a simple but powerful pattern: 79Arrange-Act-Assert. This is a great way to structure test cases and 80defines an order of operations. 81 82- Arrange inputs and targets: At the start of the test, arrange the data 83 that allows a function to work. Example: initialize a statement or 84 object. 85- Act on the target behavior: Call your function/code under test. 86- Assert expected outcome: Verify that the result (or resulting state) is as 87 expected. 88 89Unit Testing Advantages 90----------------------- 91 92- Increases testing speed and development in the long run. 93- Detects bugs at initial stage and therefore decreases bug fix cost 94 compared to acceptance testing. 95- Improves code quality. 96- Encourages writing testable code. 97 98How do I use it? 99================ 100 101* Documentation/dev-tools/kunit/start.rst - for KUnit new users. 102* Documentation/dev-tools/kunit/architecture.rst - KUnit architecture. 103* Documentation/dev-tools/kunit/run_wrapper.rst - run kunit_tool. 104* Documentation/dev-tools/kunit/run_manual.rst - run tests without kunit_tool. 105* Documentation/dev-tools/kunit/usage.rst - write tests. 106* Documentation/dev-tools/kunit/tips.rst - best practices with 107 examples. 108* Documentation/dev-tools/kunit/api/index.rst - KUnit APIs 109 used for testing. 110* Documentation/dev-tools/kunit/kunit-tool.rst - kunit_tool helper 111 script. 112* Documentation/dev-tools/kunit/faq.rst - KUnit common questions and 113 answers.