1 .. SPDX-License-Identifier: GPL-2.0 2 3 =========================== 4 Test Style and Nomenclature 5 =========================== 6 7 To make finding, writing, and using KUnit tests as simple as possible, it is 8 strongly encouraged that they are named and written according to the guidelines 9 below. While it is possible to write KUnit tests which do not follow these rules, 10 they may break some tooling, may conflict with other tests, and may not be run 11 automatically by testing systems. 12 13 It is recommended that you only deviate from these guidelines when: 14 15 1. Porting tests to KUnit which are already known with an existing name. 16 2. 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 20 Subsystems, Suites, and Tests 21 ============================= 22 23 To make tests easy to find, they are grouped into suites and subsystems. A test 24 suite is a group of tests which test a related area of the kernel. A subsystem 25 is a set of test suites which test different parts of a kernel subsystem 26 or a driver. 27 28 Subsystems 29 ---------- 30 31 Every test suite must belong to a subsystem. A subsystem is a collection of one 32 or more KUnit test suites which test the same driver or part of the kernel. A 33 test subsystem should match a single kernel module. If the code being tested 34 cannot be compiled as a module, in many cases the subsystem should correspond to 35 a directory in the source tree or an entry in the ``MAINTAINERS`` file. If 36 unsure, follow the conventions set by tests in similar areas. 37 38 Test subsystems should be named after the code being tested, either after the 39 module (wherever possible), or after the directory or files being tested. Test 40 subsystems should be named to avoid ambiguity where necessary. 41 42 If a test subsystem name has multiple components, they should be separated by 43 underscores. *Do not* include "test" or "kunit" directly in the subsystem name 44 unless we are actually testing other tests or the kunit framework itself. For 45 example, 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 57 Avoid 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 76 Suites 77 ------ 78 79 KUnit tests are grouped into test suites, which cover a specific area of 80 functionality being tested. Test suites can have shared initialization and 81 shutdown code which is run for all tests in the suite. Not all subsystems need 82 to be split into multiple test suites (for example, simple drivers). 83 84 Test suites are named after the subsystem they are part of. If a subsystem 85 contains several suites, the specific area under test should be appended to the 86 subsystem name, separated by an underscore. 87 88 In the event that there are multiple types of test using KUnit within a 89 subsystem (for example, both unit tests and integration tests), they should be 90 put into separate suites, with the type of test as the last element in the suite 91 name. Unless these tests are actually present, avoid using ``_test``, ``_unittest`` 92 or similar in the suite name. 93 94 The full test suite name (including the subsystem name) should be specified as 95 the ``.name`` member of the ``kunit_suite`` struct, and forms the base for the 96 module 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. 107 108 Avoid 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. 120 121 Test Cases 122 ---------- 123 124 Individual tests consist of a single function which tests a constrained 125 codepath, property, or function. In the test output, an individual test's 126 results will show up as subtests of the suite's results. 127 128 Tests should be named after what they are testing. This is often the name of the 129 function being tested, with a description of the input or codepath being tested. 130 As tests are C functions, they should be named and written in accordance with 131 the 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. 138 139 Example 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. 146 147 148 Should it be necessary to refer to a test outside the context of its test suite, 149 the *fully-qualified* name of a test should be the suite name followed by the 150 test name, separated by a colon (i.e. ``suite:test``). 151 152 Test Kconfig Entries 153 ==================== 154 155 Every test suite should be tied to a Kconfig entry. 156 157 This 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. 167 168 If we are not able to meet above conditions (for example, the test is unable to 169 be built as a module), Kconfig entries for tests should be tristate. 170 171 For 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. 186 187 188 Test File and Module Names 189 ========================== 190 191 KUnit tests are often compiled as a separate module. To avoid conflicting 192 with regular modules, KUnit modules should be named after the test suite, 193 followed by ``_kunit`` (e.g. if "foobar" is the core module, then 194 "foobar_kunit" is the KUnit test module). 195 196 Test source files, whether compiled as a separate module or an 197 ``#include`` in another source file, are best kept in a ``tests/`` 198 subdirectory to not conflict with other source files (e.g. for 199 tab-completion). 200 201 Note that the ``_test`` suffix has also been used in some existing 202 tests. The ``_kunit`` suffix is preferred, as it makes the distinction 203 between KUnit and non-KUnit tests clearer. 204 205 So for the common case, name the file containing the test suite 206 ``tests/<suite>_kunit.c``. The ``tests`` directory should be placed at 207 the same level as the code under test. For example, tests for 208 ``lib/string.c`` live in ``lib/tests/string_kunit.c``. 209 210 If the suite name contains some or all of the name of the test's parent 211 directory, it may make sense to modify the source filename to reduce 212 redundancy. For example, a ``foo_firmware`` suite could be in the 213 ``foo/tests/firmware_kunit.c`` file.
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