As discussed in [1], KUnit tests have hitherto not had a particularly consistent naming scheme. This adds documentation outlining how tests and test suites should be named, including how those names should be used in Kconfig entries and filenames.
[1]: https://lore.kernel.org/linux-kselftest/202006141005.BA19A9D3@keescook/t/#u
Signed-off-by: David Gow davidgow@google.com Reviewed-by: Kees Cook keescook@chromium.org --- This is a follow-up v1 to the RFC patch here: https://lore.kernel.org/linux-kselftest/20200620054944.167330-1-davidgow@goo...
There weren't any fundamental objections to the naming guidelines themselves, so nothing's changed on that front.
Otherwise, changes since the RFC: - Fixed a bit of space/tab confusion in the index (Thanks, Randy) - Added some more examples (and some test case examples). - Added some examples of what not to call subsystems and suites. - No longer explicitly require "If unsure, put N" in Kconfig entries. - Minor formatting changes.
Cheers, -- David
Documentation/dev-tools/kunit/index.rst | 1 + Documentation/dev-tools/kunit/style.rst | 181 ++++++++++++++++++++++++ 2 files changed, 182 insertions(+) create mode 100644 Documentation/dev-tools/kunit/style.rst
diff --git a/Documentation/dev-tools/kunit/index.rst b/Documentation/dev-tools/kunit/index.rst index e93606ecfb01..c234a3ab3c34 100644 --- a/Documentation/dev-tools/kunit/index.rst +++ b/Documentation/dev-tools/kunit/index.rst @@ -11,6 +11,7 @@ KUnit - Unit Testing for the Linux Kernel usage kunit-tool api/index + style faq
What is KUnit? diff --git a/Documentation/dev-tools/kunit/style.rst b/Documentation/dev-tools/kunit/style.rst new file mode 100644 index 000000000000..8cad2627924c --- /dev/null +++ b/Documentation/dev-tools/kunit/style.rst @@ -0,0 +1,181 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========================== +Test Style and Nomenclature +=========================== + +Subsystems, Suites, and Tests +============================= + +In order to make tests as easy to find as possible, they're grouped into suites +and subsystems. A test suite is a group of tests which test a related area of +the kernel, and a subsystem is a set of test suites which test different parts +of the same kernel subsystem or driver. + +Subsystems +---------- + +Every test suite must belong to a subsystem. A subsystem is a collection of one +or more KUnit test suites which test the same driver or part of the kernel. A +rule of thumb is that a test subsystem should match a single kernel module. If +the code being tested can't be compiled as a module, in many cases the subsystem +should correspond to a directory in the source tree or an entry in the +MAINTAINERS file. If unsure, follow the conventions set by tests in similar +areas. + +Test subsystems should be named after the code being tested, either after the +module (wherever possible), or after the directory or files being tested. Test +subsystems should be named to avoid ambiguity where necessary. + +If a test subsystem name has multiple components, they should be separated by +underscores. *Do not* include "test" or "kunit" directly in the subsystem name +unless you are actually testing other tests or the kunit framework itself. + +Example subsystems could be: + +``ext4`` + Matches the module and filesystem name. +``apparmor`` + Matches the module name and LSM name. +``kasan`` + Common name for the tool, prominent part of the path ``mm/kasan`` +``snd_hda_codec_hdmi`` + Has several components (``snd``, ``hda``, ``codec``, ``hdmi``) separated by + underscores. Matches the module name. + +Avoid names like these: + +``linear-ranges`` + Names should use underscores, not dashes, to separate words. Prefer + ``linear_ranges``. +``qos-kunit-test`` + As well as using underscores, this name should not have "kunit-test" as a + suffix, and ``qos`` is ambiguous as a subsystem name. ``power_qos`` would be a + better name. +``pc_parallel_port`` + The corresponding module name is ``parport_pc``, so this subsystem should also + be named ``parport_pc``. + +.. note:: + The KUnit API and tools do not explicitly know about subsystems. They're + simply a way of categorising test suites and naming modules which + provides a simple, consistent way for humans to find and run tests. This + may change in the future, though. + +Suites +------ + +KUnit tests are grouped into test suites, which cover a specific area of +functionality being tested. Test suites can have shared initialisation and +shutdown code which is run for all tests in the suite. +Not all subsystems will need to be split into multiple test suites (e.g. simple drivers). + +Test suites are named after the subsystem they are part of. If a subsystem +contains several suites, the specific area under test should be appended to the +subsystem name, separated by an underscore. + +The full test suite name (including the subsystem name) should be specified as +the ``.name`` member of the ``kunit_suite`` struct, and forms the base for the +module name (see below). + +Example test suites could include: + +``ext4_inode`` + Part of the ``ext4`` subsystem, testing the ``inode`` area. +``kunit_try_catch`` + Part of the ``kunit`` implementation itself, testing the ``try_catch`` area. +``apparmor_property_entry`` + Part of the ``apparmor`` subsystem, testing the ``property_entry`` area. +``kasan`` + The ``kasan`` subsystem has only one suite, so the suite name is the same as + the subsystem name. + +Avoid names like: + +``ext4_ext4_inode`` + There's no reason to state the subsystem twice. +``property_entry`` + The suite name is ambiguous without the subsystem name. +``kasan_unit_test`` + Because there is only one suite in the ``kasan`` subsystem, the suite should + just be called ``kasan``. There's no need to redundantly add ``unit_test``. + +Test Cases +---------- + +Individual tests consist of a single function which tests a constrained +codepath, property, or function. In the test output, individual tests' results +will show up as subtests of the suite's results. + +Tests should be named after what they're testing. This is often the name of the +function being tested, with a description of the input or codepath being tested. +As tests are C functions, they should be named and written in accordance with +the kernel coding style. + +.. note:: + As tests are themselves functions, their names cannot conflict with + other C identifiers in the kernel. This may require some creative + naming. It's a good idea to make your test functions `static` to avoid + polluting the global namespace. + +Example test names include: + +``unpack_u32_with_null_name`` + Tests the ``unpack_u32`` function when a NULL name is passed in. +``test_list_splice`` + Tests the ``list_splice`` macro. It has the prefix ``test_`` to avoid a + name conflict with the macro itself. + + +Should it be necessary to refer to a test outside the context of its test suite, +the *fully-qualified* name of a test should be the suite name followed by the +test name, separated by a colon (i.e. ``suite:test``). + +Test Kconfig Entries +==================== + +Every test suite should be tied to a Kconfig entry. + +This Kconfig entry must: + +* be named ``CONFIG_<name>_KUNIT_TEST``: where <name> is the name of the test + suite. +* be listed either alongside the config entries for the driver/subsystem being + tested, or be under [Kernel Hacking]→[Kernel Testing and Coverage] +* depend on ``CONFIG_KUNIT`` +* be visible only if ``CONFIG_KUNIT_ALL_TESTS`` is not enabled. +* have a default value of ``CONFIG_KUNIT_ALL_TESTS``. +* have a brief description of KUnit in the help text + +Unless there's a specific reason not to (e.g. the test is unable to be built as +a module), Kconfig entries for tests should be tristate. + +An example Kconfig entry: + +.. code-block:: none + + config FOO_KUNIT_TEST + tristate "KUnit test for foo" if !KUNIT_ALL_TESTS + depends on KUNIT + default KUNIT_ALL_TESTS + help + This builds unit tests for foo. + + For more information on KUnit and unit tests in general, please refer + to the KUnit documentation in Documentation/dev-tools/kunit + + If unsure, say N + + +Test Filenames +============== + +Where possible, test suites should be placed in a separate source file in the +same directory as the code being tested. + +This file should be named ``<suite>_kunit.c``. It may make sense to strip +excessive namespacing from the source filename (e.g., ``firmware_kunit.c`` instead of +``<drivername>_firmware.c``), but please ensure the module name does contain the +full suite name. + +