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| 3 | ===========================
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| 4 | Test Style and Nomenclature
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| 5 | ===========================
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| 6 |
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| 7 | To make finding, writing, and using KUnit tests as simple as possible, it is
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| 8 | strongly encouraged that they are named and written according to the guidelines
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| 9 | below. While it is possible to write KUnit tests which do not follow these rules,
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| 10 | they may break some tooling, may conflict with other tests, and may not be run
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| 11 | automatically by testing systems.
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| 12 |
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| 13 | It is recommended that you only deviate from these guidelines when:
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| 14 |
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| 15 | 1. Porting tests to KUnit which are already known with an existing name.
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| 16 | 2. Writing tests which would cause serious problems if automatically run. For
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| 17 | example, non-deterministically producing false positives or negatives, or
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| 18 | taking a long time to run.
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| 19 |
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| 20 | Subsystems, Suites, and Tests
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| 21 | =============================
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| 22 |
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| 23 | To make tests easy to find, they are grouped into suites and subsystems. A test
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| 24 | suite is a group of tests which test a related area of the kernel. A subsystem
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| 25 | is a set of test suites which test different parts of a kernel subsystem
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| 26 | or a driver.
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| 27 |
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| 28 | Subsystems
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| 29 | ----------
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| 30 |
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| 31 | Every test suite must belong to a subsystem. A subsystem is a collection of one
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| 32 | or more KUnit test suites which test the same driver or part of the kernel. A
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| 33 | test subsystem should match a single kernel module. If the code being tested
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| 34 | cannot be compiled as a module, in many cases the subsystem should correspond to
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| 35 | a directory in the source tree or an entry in the ``MAINTAINERS`` file. If
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| 36 | unsure, follow the conventions set by tests in similar areas.
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| 37 |
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| 38 | Test subsystems should be named after the code being tested, either after the
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| 39 | module (wherever possible), or after the directory or files being tested. Test
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| 40 | subsystems should be named to avoid ambiguity where necessary.
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| 41 |
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| 42 | If a test subsystem name has multiple components, they should be separated by
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| 43 | underscores. *Do not* include "test" or "kunit" directly in the subsystem name
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| 44 | unless we are actually testing other tests or the kunit framework itself. For
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| 45 | example, subsystems could be called:
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| 46 |
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| 47 | ``ext4``
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| 48 | Matches the module and filesystem name.
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| 49 | ``apparmor``
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| 50 | Matches the module name and LSM name.
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| 51 | ``kasan``
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| 52 | Common name for the tool, prominent part of the path ``mm/kasan``
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| 53 | ``snd_hda_codec_hdmi``
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| 54 | Has several components (``snd``, ``hda``, ``codec``, ``hdmi``) separated by
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| 55 | underscores. Matches the module name.
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| 56 |
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| 57 | Avoid names as shown in examples below:
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| 58 |
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| 59 | ``linear-ranges``
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| 60 | Names should use underscores, not dashes, to separate words. Prefer
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| 61 | ``linear_ranges``.
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| 62 | ``qos-kunit-test``
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| 63 | This name should use underscores, and not have "kunit-test" as a
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| 64 | suffix. ``qos`` is also ambiguous as a subsystem name, because several parts
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| 65 | of the kernel have a ``qos`` subsystem. ``power_qos`` would be a better name.
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| 66 | ``pc_parallel_port``
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| 67 | The corresponding module name is ``parport_pc``, so this subsystem should also
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| 68 | be named ``parport_pc``.
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| 69 |
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| 70 | .. note::
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| 71 | The KUnit API and tools do not explicitly know about subsystems. They are
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| 72 | a way of categorizing test suites and naming modules which provides a
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| 73 | simple, consistent way for humans to find and run tests. This may change
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| 74 | in the future.
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| 75 |
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| 76 | Suites
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| 77 | ------
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| 78 |
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| 79 | KUnit tests are grouped into test suites, which cover a specific area of
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| 80 | functionality being tested. Test suites can have shared initialization and
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| 81 | shutdown code which is run for all tests in the suite. Not all subsystems need
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| 82 | to be split into multiple test suites (for example, simple drivers).
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| 83 |
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| 84 | Test suites are named after the subsystem they are part of. If a subsystem
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| 85 | contains several suites, the specific area under test should be appended to the
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| 86 | subsystem name, separated by an underscore.
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| 87 |
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| 88 | In the event that there are multiple types of test using KUnit within a
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| 89 | subsystem (for example, both unit tests and integration tests), they should be
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| 90 | put into separate suites, with the type of test as the last element in the suite
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| 91 | name. Unless these tests are actually present, avoid using ``_test``, ``_unittest``
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| 92 | or similar in the suite name.
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| 93 |
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| 94 | The full test suite name (including the subsystem name) should be specified as
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| 95 | the ``.name`` member of the ``kunit_suite`` struct, and forms the base for the
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| 96 | module name. For example, test suites could include:
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| 97 |
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| 98 | ``ext4_inode``
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| 99 | Part of the ``ext4`` subsystem, testing the ``inode`` area.
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| 100 | ``kunit_try_catch``
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| 101 | Part of the ``kunit`` implementation itself, testing the ``try_catch`` area.
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| 102 | ``apparmor_property_entry``
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| 103 | Part of the ``apparmor`` subsystem, testing the ``property_entry`` area.
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| 104 | ``kasan``
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| 105 | The ``kasan`` subsystem has only one suite, so the suite name is the same as
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| 106 | the subsystem name.
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| 107 |
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| 108 | Avoid names, for example:
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| 109 |
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| 110 | ``ext4_ext4_inode``
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| 111 | There is no reason to state the subsystem twice.
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| 112 | ``property_entry``
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| 113 | The suite name is ambiguous without the subsystem name.
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| 114 | ``kasan_integration_test``
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| 115 | Because there is only one suite in the ``kasan`` subsystem, the suite should
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| 116 | just be called as ``kasan``. Do not redundantly add
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| 117 | ``integration_test``. It should be a separate test suite. For example, if the
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| 118 | unit tests are added, then that suite could be named as ``kasan_unittest`` or
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| 119 | similar.
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| 120 |
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| 121 | Test Cases
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| 122 | ----------
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| 123 |
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| 124 | Individual tests consist of a single function which tests a constrained
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| 125 | codepath, property, or function. In the test output, an individual test's
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| 126 | results will show up as subtests of the suite's results.
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| 127 |
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| 128 | Tests should be named after what they are testing. This is often the name of the
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| 129 | function being tested, with a description of the input or codepath being tested.
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| 130 | As tests are C functions, they should be named and written in accordance with
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| 131 | the kernel coding style.
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| 132 |
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| 133 | .. note::
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| 134 | As tests are themselves functions, their names cannot conflict with
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| 135 | other C identifiers in the kernel. This may require some creative
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| 136 | naming. It is a good idea to make your test functions `static` to avoid
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| 137 | polluting the global namespace.
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| 138 |
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| 139 | Example test names include:
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| 140 |
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| 141 | ``unpack_u32_with_null_name``
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| 142 | Tests the ``unpack_u32`` function when a NULL name is passed in.
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| 143 | ``test_list_splice``
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| 144 | Tests the ``list_splice`` macro. It has the prefix ``test_`` to avoid a
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| 145 | name conflict with the macro itself.
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| 146 |
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| 147 |
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| 148 | Should it be necessary to refer to a test outside the context of its test suite,
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| 149 | the *fully-qualified* name of a test should be the suite name followed by the
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| 150 | test name, separated by a colon (i.e. ``suite:test``).
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| 151 |
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| 152 | Test Kconfig Entries
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| 153 | ====================
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| 154 |
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| 155 | Every test suite should be tied to a Kconfig entry.
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| 156 |
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| 157 | This Kconfig entry must:
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| 158 |
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| 159 | * be named ``CONFIG_<name>_KUNIT_TEST``: where <name> is the name of the test
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| 160 | suite.
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| 161 | * be listed either alongside the config entries for the driver/subsystem being
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| 162 | tested, or be under [Kernel Hacking]->[Kernel Testing and Coverage]
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| 163 | * depend on ``CONFIG_KUNIT``.
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| 164 | * be visible only if ``CONFIG_KUNIT_ALL_TESTS`` is not enabled.
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| 165 | * have a default value of ``CONFIG_KUNIT_ALL_TESTS``.
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| 166 | * have a brief description of KUnit in the help text.
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| 167 | * depend on the feature being tested, rather than selecting it (so that
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| 168 | enabling ``CONFIG_KUNIT_ALL_TESTS`` does not enable unrelated functionality).
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| 169 | * be ``tristate``, unless there is a specific reason that the test cannot be
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| 170 | built as a module.
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| 171 |
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| 172 | For example, a Kconfig entry might look like:
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| 173 |
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| 174 | .. code-block:: none
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| 175 |
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| 176 | config FOO_KUNIT_TEST
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| 177 | tristate "KUnit test for foo" if !KUNIT_ALL_TESTS
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| 178 | depends on KUNIT
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| 179 | default KUNIT_ALL_TESTS
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| 180 | help
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| 181 | This builds unit tests for foo.
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| 182 |
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| 183 | For more information on KUnit and unit tests in general,
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| 184 | please refer to the KUnit documentation in Documentation/dev-tools/kunit/.
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| 185 |
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| 186 | If unsure, say N.
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| 187 |
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| 188 |
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| 189 | Test File and Module Names
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| 190 | ==========================
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| 191 |
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| 192 | KUnit tests are often compiled as a separate module. To avoid conflicting
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| 193 | with regular modules, KUnit modules should be named after the test suite,
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| 194 | followed by ``_kunit`` (e.g. if "foobar" is the core module, then
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| 195 | "foobar_kunit" is the KUnit test module).
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| 196 |
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| 197 | Test source files, whether compiled as a separate module or an
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| 198 | ``#include`` in another source file, are best kept in a ``tests/``
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| 199 | subdirectory to not conflict with other source files (e.g. for
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| 200 | tab-completion).
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| 201 |
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| 202 | Note that the ``_test`` suffix has also been used in some existing
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| 203 | tests. The ``_kunit`` suffix is preferred, as it makes the distinction
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| 204 | between KUnit and non-KUnit tests clearer.
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| 205 |
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| 206 | So for the common case, name the file containing the test suite
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| 207 | ``tests/<suite>_kunit.c``. The ``tests`` directory should be placed at
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| 208 | the same level as the code under test. For example, tests for
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| 209 | ``lib/string.c`` live in ``lib/tests/string_kunit.c``.
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| 210 |
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| 211 | If the suite name contains some or all of the name of the test's parent
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| 212 | directory, it may make sense to modify the source filename to reduce
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| 213 | redundancy. For example, a ``foo_firmware`` suite could be in the
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| 214 | ``foo/tests/firmware_kunit.c`` file.
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