style.rst 8.0 KB

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  1. .. SPDX-License-Identifier: GPL-2.0
  2. ===========================
  3. Test Style and Nomenclature
  4. ===========================
  5. To make finding, writing, and using KUnit tests as simple as possible, it's
  6. strongly encouraged that they are named and written according to the guidelines
  7. below. While it's possible to write KUnit tests which do not follow these rules,
  8. they may break some tooling, may conflict with other tests, and may not be run
  9. automatically by testing systems.
  10. It's recommended that you only deviate from these guidelines when:
  11. 1. Porting tests to KUnit which are already known with an existing name, or
  12. 2. Writing tests which would cause serious problems if automatically run (e.g.,
  13. non-deterministically producing false positives or negatives, or taking an
  14. extremely long time to run).
  15. Subsystems, Suites, and Tests
  16. =============================
  17. In order to make tests as easy to find as possible, they're grouped into suites
  18. and subsystems. A test suite is a group of tests which test a related area of
  19. the kernel, and a subsystem is a set of test suites which test different parts
  20. of the same kernel subsystem or driver.
  21. Subsystems
  22. ----------
  23. Every test suite must belong to a subsystem. A subsystem is a collection of one
  24. or more KUnit test suites which test the same driver or part of the kernel. A
  25. rule of thumb is that a test subsystem should match a single kernel module. If
  26. the code being tested can't be compiled as a module, in many cases the subsystem
  27. should correspond to a directory in the source tree or an entry in the
  28. MAINTAINERS file. If unsure, follow the conventions set by tests in similar
  29. areas.
  30. Test subsystems should be named after the code being tested, either after the
  31. module (wherever possible), or after the directory or files being tested. Test
  32. subsystems should be named to avoid ambiguity where necessary.
  33. If a test subsystem name has multiple components, they should be separated by
  34. underscores. *Do not* include "test" or "kunit" directly in the subsystem name
  35. unless you are actually testing other tests or the kunit framework itself.
  36. Example subsystems could be:
  37. ``ext4``
  38. Matches the module and filesystem name.
  39. ``apparmor``
  40. Matches the module name and LSM name.
  41. ``kasan``
  42. Common name for the tool, prominent part of the path ``mm/kasan``
  43. ``snd_hda_codec_hdmi``
  44. Has several components (``snd``, ``hda``, ``codec``, ``hdmi``) separated by
  45. underscores. Matches the module name.
  46. Avoid names like these:
  47. ``linear-ranges``
  48. Names should use underscores, not dashes, to separate words. Prefer
  49. ``linear_ranges``.
  50. ``qos-kunit-test``
  51. As well as using underscores, this name should not have "kunit-test" as a
  52. suffix, and ``qos`` is ambiguous as a subsystem name. ``power_qos`` would be a
  53. better name.
  54. ``pc_parallel_port``
  55. The corresponding module name is ``parport_pc``, so this subsystem should also
  56. be named ``parport_pc``.
  57. .. note::
  58. The KUnit API and tools do not explicitly know about subsystems. They're
  59. simply a way of categorising test suites and naming modules which
  60. provides a simple, consistent way for humans to find and run tests. This
  61. may change in the future, though.
  62. Suites
  63. ------
  64. KUnit tests are grouped into test suites, which cover a specific area of
  65. functionality being tested. Test suites can have shared initialisation and
  66. shutdown code which is run for all tests in the suite.
  67. Not all subsystems will need to be split into multiple test suites (e.g. simple drivers).
  68. Test suites are named after the subsystem they are part of. If a subsystem
  69. contains several suites, the specific area under test should be appended to the
  70. subsystem name, separated by an underscore.
  71. In the event that there are multiple types of test using KUnit within a
  72. subsystem (e.g., both unit tests and integration tests), they should be put into
  73. separate suites, with the type of test as the last element in the suite name.
  74. Unless these tests are actually present, avoid using ``_test``, ``_unittest`` or
  75. similar in the suite name.
  76. The full test suite name (including the subsystem name) should be specified as
  77. the ``.name`` member of the ``kunit_suite`` struct, and forms the base for the
  78. module name (see below).
  79. Example test suites could include:
  80. ``ext4_inode``
  81. Part of the ``ext4`` subsystem, testing the ``inode`` area.
  82. ``kunit_try_catch``
  83. Part of the ``kunit`` implementation itself, testing the ``try_catch`` area.
  84. ``apparmor_property_entry``
  85. Part of the ``apparmor`` subsystem, testing the ``property_entry`` area.
  86. ``kasan``
  87. The ``kasan`` subsystem has only one suite, so the suite name is the same as
  88. the subsystem name.
  89. Avoid names like:
  90. ``ext4_ext4_inode``
  91. There's no reason to state the subsystem twice.
  92. ``property_entry``
  93. The suite name is ambiguous without the subsystem name.
  94. ``kasan_integration_test``
  95. Because there is only one suite in the ``kasan`` subsystem, the suite should
  96. just be called ``kasan``. There's no need to redundantly add
  97. ``integration_test``. Should a separate test suite with, for example, unit
  98. tests be added, then that suite could be named ``kasan_unittest`` or similar.
  99. Test Cases
  100. ----------
  101. Individual tests consist of a single function which tests a constrained
  102. codepath, property, or function. In the test output, individual tests' results
  103. will show up as subtests of the suite's results.
  104. Tests should be named after what they're testing. This is often the name of the
  105. function being tested, with a description of the input or codepath being tested.
  106. As tests are C functions, they should be named and written in accordance with
  107. the kernel coding style.
  108. .. note::
  109. As tests are themselves functions, their names cannot conflict with
  110. other C identifiers in the kernel. This may require some creative
  111. naming. It's a good idea to make your test functions `static` to avoid
  112. polluting the global namespace.
  113. Example test names include:
  114. ``unpack_u32_with_null_name``
  115. Tests the ``unpack_u32`` function when a NULL name is passed in.
  116. ``test_list_splice``
  117. Tests the ``list_splice`` macro. It has the prefix ``test_`` to avoid a
  118. name conflict with the macro itself.
  119. Should it be necessary to refer to a test outside the context of its test suite,
  120. the *fully-qualified* name of a test should be the suite name followed by the
  121. test name, separated by a colon (i.e. ``suite:test``).
  122. Test Kconfig Entries
  123. ====================
  124. Every test suite should be tied to a Kconfig entry.
  125. This Kconfig entry must:
  126. * be named ``CONFIG_<name>_KUNIT_TEST``: where <name> is the name of the test
  127. suite.
  128. * be listed either alongside the config entries for the driver/subsystem being
  129. tested, or be under [Kernel Hacking]→[Kernel Testing and Coverage]
  130. * depend on ``CONFIG_KUNIT``
  131. * be visible only if ``CONFIG_KUNIT_ALL_TESTS`` is not enabled.
  132. * have a default value of ``CONFIG_KUNIT_ALL_TESTS``.
  133. * have a brief description of KUnit in the help text
  134. Unless there's a specific reason not to (e.g. the test is unable to be built as
  135. a module), Kconfig entries for tests should be tristate.
  136. An example Kconfig entry:
  137. .. code-block:: none
  138. config FOO_KUNIT_TEST
  139. tristate "KUnit test for foo" if !KUNIT_ALL_TESTS
  140. depends on KUNIT
  141. default KUNIT_ALL_TESTS
  142. help
  143. This builds unit tests for foo.
  144. For more information on KUnit and unit tests in general, please refer
  145. to the KUnit documentation in Documentation/dev-tools/kunit/.
  146. If unsure, say N.
  147. Test File and Module Names
  148. ==========================
  149. KUnit tests can often be compiled as a module. These modules should be named
  150. after the test suite, followed by ``_test``. If this is likely to conflict with
  151. non-KUnit tests, the suffix ``_kunit`` can also be used.
  152. The easiest way of achieving this is to name the file containing the test suite
  153. ``<suite>_test.c`` (or, as above, ``<suite>_kunit.c``). This file should be
  154. placed next to the code under test.
  155. If the suite name contains some or all of the name of the test's parent
  156. directory, it may make sense to modify the source filename to reduce redundancy.
  157. For example, a ``foo_firmware`` suite could be in the ``foo/firmware_test.c``
  158. file.