1.. SPDX-License-Identifier: GPL-2.0 2 3=========================== 4Test Style and Nomenclature 5=========================== 6 7To make finding, writing, and using KUnit tests as simple as possible, it is 8strongly encouraged that they are named and written according to the guidelines 9below. While it is possible to write KUnit tests which do not follow these rules, 10they may break some tooling, may conflict with other tests, and may not be run 11automatically by testing systems. 12 13It is recommended that you only deviate from these guidelines when: 14 151. Porting tests to KUnit which are already known with an existing name. 162. Writing tests which would cause serious problems if automatically run. For 17 example, non-deterministically producing false positives or negatives, or 18 taking a long time to run. 19 20Subsystems, Suites, and Tests 21============================= 22 23To make tests easy to find, they are grouped into suites and subsystems. A test 24suite is a group of tests which test a related area of the kernel. A subsystem 25is a set of test suites which test different parts of a kernel subsystem 26or a driver. 27 28Subsystems 29---------- 30 31Every test suite must belong to a subsystem. A subsystem is a collection of one 32or more KUnit test suites which test the same driver or part of the kernel. A 33test subsystem should match a single kernel module. If the code being tested 34cannot be compiled as a module, in many cases the subsystem should correspond to 35a directory in the source tree or an entry in the ``MAINTAINERS`` file. If 36unsure, follow the conventions set by tests in similar areas. 37 38Test subsystems should be named after the code being tested, either after the 39module (wherever possible), or after the directory or files being tested. Test 40subsystems should be named to avoid ambiguity where necessary. 41 42If a test subsystem name has multiple components, they should be separated by 43underscores. *Do not* include "test" or "kunit" directly in the subsystem name 44unless we are actually testing other tests or the kunit framework itself. For 45example, subsystems could be called: 46 47``ext4`` 48 Matches the module and filesystem name. 49``apparmor`` 50 Matches the module name and LSM name. 51``kasan`` 52 Common name for the tool, prominent part of the path ``mm/kasan`` 53``snd_hda_codec_hdmi`` 54 Has several components (``snd``, ``hda``, ``codec``, ``hdmi``) separated by 55 underscores. Matches the module name. 56 57Avoid names as shown in examples below: 58 59``linear-ranges`` 60 Names should use underscores, not dashes, to separate words. Prefer 61 ``linear_ranges``. 62``qos-kunit-test`` 63 This name should use underscores, and not have "kunit-test" as a 64 suffix. ``qos`` is also ambiguous as a subsystem name, because several parts 65 of the kernel have a ``qos`` subsystem. ``power_qos`` would be a better name. 66``pc_parallel_port`` 67 The corresponding module name is ``parport_pc``, so this subsystem should also 68 be named ``parport_pc``. 69 70.. note:: 71 The KUnit API and tools do not explicitly know about subsystems. They are 72 a way of categorizing test suites and naming modules which provides a 73 simple, consistent way for humans to find and run tests. This may change 74 in the future. 75 76Suites 77------ 78 79KUnit tests are grouped into test suites, which cover a specific area of 80functionality being tested. Test suites can have shared initialization and 81shutdown code which is run for all tests in the suite. Not all subsystems need 82to be split into multiple test suites (for example, simple drivers). 83 84Test suites are named after the subsystem they are part of. If a subsystem 85contains several suites, the specific area under test should be appended to the 86subsystem name, separated by an underscore. 87 88In the event that there are multiple types of test using KUnit within a 89subsystem (for example, both unit tests and integration tests), they should be 90put into separate suites, with the type of test as the last element in the suite 91name. Unless these tests are actually present, avoid using ``_test``, ``_unittest`` 92or similar in the suite name. 93 94The full test suite name (including the subsystem name) should be specified as 95the ``.name`` member of the ``kunit_suite`` struct, and forms the base for the 96module name. For example, test suites could include: 97 98``ext4_inode`` 99 Part of the ``ext4`` subsystem, testing the ``inode`` area. 100``kunit_try_catch`` 101 Part of the ``kunit`` implementation itself, testing the ``try_catch`` area. 102``apparmor_property_entry`` 103 Part of the ``apparmor`` subsystem, testing the ``property_entry`` area. 104``kasan`` 105 The ``kasan`` subsystem has only one suite, so the suite name is the same as 106 the subsystem name. 107 108Avoid names, for example: 109 110``ext4_ext4_inode`` 111 There is no reason to state the subsystem twice. 112``property_entry`` 113 The suite name is ambiguous without the subsystem name. 114``kasan_integration_test`` 115 Because there is only one suite in the ``kasan`` subsystem, the suite should 116 just be called as ``kasan``. Do not redundantly add 117 ``integration_test``. It should be a separate test suite. For example, if the 118 unit tests are added, then that suite could be named as ``kasan_unittest`` or 119 similar. 120 121Test Cases 122---------- 123 124Individual tests consist of a single function which tests a constrained 125codepath, property, or function. In the test output, an individual test's 126results will show up as subtests of the suite's results. 127 128Tests should be named after what they are testing. This is often the name of the 129function being tested, with a description of the input or codepath being tested. 130As tests are C functions, they should be named and written in accordance with 131the kernel coding style. 132 133.. note:: 134 As tests are themselves functions, their names cannot conflict with 135 other C identifiers in the kernel. This may require some creative 136 naming. It is a good idea to make your test functions `static` to avoid 137 polluting the global namespace. 138 139Example test names include: 140 141``unpack_u32_with_null_name`` 142 Tests the ``unpack_u32`` function when a NULL name is passed in. 143``test_list_splice`` 144 Tests the ``list_splice`` macro. It has the prefix ``test_`` to avoid a 145 name conflict with the macro itself. 146 147 148Should it be necessary to refer to a test outside the context of its test suite, 149the *fully-qualified* name of a test should be the suite name followed by the 150test name, separated by a colon (i.e. ``suite:test``). 151 152Test Kconfig Entries 153==================== 154 155Every test suite should be tied to a Kconfig entry. 156 157This Kconfig entry must: 158 159* be named ``CONFIG_<name>_KUNIT_TEST``: where <name> is the name of the test 160 suite. 161* be listed either alongside the config entries for the driver/subsystem being 162 tested, or be under [Kernel Hacking]->[Kernel Testing and Coverage] 163* depend on ``CONFIG_KUNIT``. 164* be visible only if ``CONFIG_KUNIT_ALL_TESTS`` is not enabled. 165* have a default value of ``CONFIG_KUNIT_ALL_TESTS``. 166* have a brief description of KUnit in the help text. 167 168If we are not able to meet above conditions (for example, the test is unable to 169be built as a module), Kconfig entries for tests should be tristate. 170 171For example, a Kconfig entry might look like: 172 173.. code-block:: none 174 175 config FOO_KUNIT_TEST 176 tristate "KUnit test for foo" if !KUNIT_ALL_TESTS 177 depends on KUNIT 178 default KUNIT_ALL_TESTS 179 help 180 This builds unit tests for foo. 181 182 For more information on KUnit and unit tests in general, 183 please refer to the KUnit documentation in Documentation/dev-tools/kunit/. 184 185 If unsure, say N. 186 187 188Test File and Module Names 189========================== 190 191KUnit tests can often be compiled as a module. These modules should be named 192after the test suite, followed by ``_test``. If this is likely to conflict with 193non-KUnit tests, the suffix ``_kunit`` can also be used. 194 195The easiest way of achieving this is to name the file containing the test suite 196``<suite>_test.c`` (or, as above, ``<suite>_kunit.c``). This file should be 197placed next to the code under test. 198 199If the suite name contains some or all of the name of the test's parent 200directory, it may make sense to modify the source filename to reduce redundancy. 201For example, a ``foo_firmware`` suite could be in the ``foo/firmware_test.c`` 202file. 203