203 lines
8.0 KiB
ReStructuredText
203 lines
8.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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===========================
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Test Style and Nomenclature
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===========================
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To make finding, writing, and using KUnit tests as simple as possible, it is
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strongly encouraged that they are named and written according to the guidelines
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below. While it is possible to write KUnit tests which do not follow these rules,
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they may break some tooling, may conflict with other tests, and may not be run
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automatically by testing systems.
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It is recommended that you only deviate from these guidelines when:
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1. Porting tests to KUnit which are already known with an existing name.
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2. Writing tests which would cause serious problems if automatically run. For
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example, non-deterministically producing false positives or negatives, or
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taking a long time to run.
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Subsystems, Suites, and Tests
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=============================
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To make tests easy to find, they are grouped into suites and subsystems. A test
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suite is a group of tests which test a related area of the kernel. A subsystem
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is a set of test suites which test different parts of a kernel subsystem
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or a driver.
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Subsystems
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----------
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Every test suite must belong to a subsystem. A subsystem is a collection of one
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or more KUnit test suites which test the same driver or part of the kernel. A
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test subsystem should match a single kernel module. If the code being tested
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cannot be compiled as a module, in many cases the subsystem should correspond to
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a directory in the source tree or an entry in the ``MAINTAINERS`` file. If
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unsure, follow the conventions set by tests in similar areas.
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Test subsystems should be named after the code being tested, either after the
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module (wherever possible), or after the directory or files being tested. Test
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subsystems should be named to avoid ambiguity where necessary.
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If a test subsystem name has multiple components, they should be separated by
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underscores. *Do not* include "test" or "kunit" directly in the subsystem name
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unless we are actually testing other tests or the kunit framework itself. For
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example, subsystems could be called:
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``ext4``
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Matches the module and filesystem name.
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``apparmor``
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Matches the module name and LSM name.
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``kasan``
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Common name for the tool, prominent part of the path ``mm/kasan``
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``snd_hda_codec_hdmi``
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Has several components (``snd``, ``hda``, ``codec``, ``hdmi``) separated by
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underscores. Matches the module name.
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Avoid names as shown in examples below:
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``linear-ranges``
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Names should use underscores, not dashes, to separate words. Prefer
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``linear_ranges``.
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``qos-kunit-test``
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This name should use underscores, and not have "kunit-test" as a
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suffix. ``qos`` is also ambiguous as a subsystem name, because several parts
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of the kernel have a ``qos`` subsystem. ``power_qos`` would be a better name.
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``pc_parallel_port``
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The corresponding module name is ``parport_pc``, so this subsystem should also
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be named ``parport_pc``.
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.. note::
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The KUnit API and tools do not explicitly know about subsystems. They are
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a way of categorizing test suites and naming modules which provides a
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simple, consistent way for humans to find and run tests. This may change
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in the future.
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Suites
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------
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KUnit tests are grouped into test suites, which cover a specific area of
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functionality being tested. Test suites can have shared initialization and
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shutdown code which is run for all tests in the suite. Not all subsystems need
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to be split into multiple test suites (for example, simple drivers).
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Test suites are named after the subsystem they are part of. If a subsystem
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contains several suites, the specific area under test should be appended to the
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subsystem name, separated by an underscore.
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In the event that there are multiple types of test using KUnit within a
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subsystem (for example, both unit tests and integration tests), they should be
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put into separate suites, with the type of test as the last element in the suite
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name. Unless these tests are actually present, avoid using ``_test``, ``_unittest``
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or similar in the suite name.
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The full test suite name (including the subsystem name) should be specified as
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the ``.name`` member of the ``kunit_suite`` struct, and forms the base for the
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module name. For example, test suites could include:
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``ext4_inode``
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Part of the ``ext4`` subsystem, testing the ``inode`` area.
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``kunit_try_catch``
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Part of the ``kunit`` implementation itself, testing the ``try_catch`` area.
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``apparmor_property_entry``
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Part of the ``apparmor`` subsystem, testing the ``property_entry`` area.
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``kasan``
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The ``kasan`` subsystem has only one suite, so the suite name is the same as
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the subsystem name.
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Avoid names, for example:
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``ext4_ext4_inode``
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There is no reason to state the subsystem twice.
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``property_entry``
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The suite name is ambiguous without the subsystem name.
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``kasan_integration_test``
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Because there is only one suite in the ``kasan`` subsystem, the suite should
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just be called as ``kasan``. Do not redundantly add
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``integration_test``. It should be a separate test suite. For example, if the
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unit tests are added, then that suite could be named as ``kasan_unittest`` or
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similar.
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Test Cases
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----------
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Individual tests consist of a single function which tests a constrained
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codepath, property, or function. In the test output, an individual test's
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results will show up as subtests of the suite's results.
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Tests should be named after what they are testing. This is often the name of the
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function being tested, with a description of the input or codepath being tested.
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As tests are C functions, they should be named and written in accordance with
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the kernel coding style.
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.. note::
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As tests are themselves functions, their names cannot conflict with
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other C identifiers in the kernel. This may require some creative
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naming. It is a good idea to make your test functions `static` to avoid
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polluting the global namespace.
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Example test names include:
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``unpack_u32_with_null_name``
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Tests the ``unpack_u32`` function when a NULL name is passed in.
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``test_list_splice``
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Tests the ``list_splice`` macro. It has the prefix ``test_`` to avoid a
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name conflict with the macro itself.
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Should it be necessary to refer to a test outside the context of its test suite,
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the *fully-qualified* name of a test should be the suite name followed by the
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test name, separated by a colon (i.e. ``suite:test``).
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Test Kconfig Entries
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====================
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Every test suite should be tied to a Kconfig entry.
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This Kconfig entry must:
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* be named ``CONFIG_<name>_KUNIT_TEST``: where <name> is the name of the test
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suite.
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* be listed either alongside the config entries for the driver/subsystem being
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tested, or be under [Kernel Hacking]->[Kernel Testing and Coverage]
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* depend on ``CONFIG_KUNIT``.
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* be visible only if ``CONFIG_KUNIT_ALL_TESTS`` is not enabled.
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* have a default value of ``CONFIG_KUNIT_ALL_TESTS``.
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* have a brief description of KUnit in the help text.
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If we are not able to meet above conditions (for example, the test is unable to
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be built as a module), Kconfig entries for tests should be tristate.
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For example, a Kconfig entry might look like:
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.. code-block:: none
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config FOO_KUNIT_TEST
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tristate "KUnit test for foo" if !KUNIT_ALL_TESTS
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depends on KUNIT
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default KUNIT_ALL_TESTS
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help
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This builds unit tests for foo.
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For more information on KUnit and unit tests in general,
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please refer to the KUnit documentation in Documentation/dev-tools/kunit/.
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If unsure, say N.
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Test File and Module Names
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==========================
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KUnit tests can often be compiled as a module. These modules should be named
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after the test suite, followed by ``_test``. If this is likely to conflict with
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non-KUnit tests, the suffix ``_kunit`` can also be used.
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The easiest way of achieving this is to name the file containing the test suite
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``<suite>_test.c`` (or, as above, ``<suite>_kunit.c``). This file should be
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placed next to the code under test.
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If the suite name contains some or all of the name of the test's parent
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directory, it may make sense to modify the source filename to reduce redundancy.
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For example, a ``foo_firmware`` suite could be in the ``foo/firmware_test.c``
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file.
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