1 .. SPDX-License-Identifier: GPL-2.0
2
3 ==================
4 KUnit Architecture
5 ==================
6
7 The KUnit architecture is divided into two parts:
8
9 - `In-Kernel Testing Framework`_
10 - `kunit_tool (Command-line Test Harness)`_
11
12 In-Kernel Testing Framework
13 ===========================
14
15 The kernel testing library supports KUnit tests written in C using
16 KUnit. These KUnit tests are kernel code. KUnit performs the following
17 tasks:
18
19 - Organizes tests
20 - Reports test results
21 - Provides test utilities
22
23 Test Cases
24 ----------
25
26 The test case is the fundamental unit in KUnit. KUnit test cases are organised
27 into suites. A KUnit test case is a function with type signature
28 ``void (*)(struct kunit *test)``. These test case functions are wrapped in a
29 struct called struct kunit_case.
30
31 .. note:
32 ``generate_params`` is optional for non-parameterized tests.
33
34 Each KUnit test case receives a ``struct kunit`` context object that tracks a
35 running test. The KUnit assertion macros and other KUnit utilities use the
36 ``struct kunit`` context object. As an exception, there are two fields:
37
38 - ``->priv``: The setup functions can use it to store arbitrary test
39 user data.
40
41 - ``->param_value``: It contains the parameter value which can be
42 retrieved in the parameterized tests.
43
44 Test Suites
45 -----------
46
47 A KUnit suite includes a collection of test cases. The KUnit suites
48 are represented by the ``struct kunit_suite``. For example:
49
50 .. code-block:: c
51
52 static struct kunit_case example_test_cases[] = {
53 KUNIT_CASE(example_test_foo),
54 KUNIT_CASE(example_test_bar),
55 KUNIT_CASE(example_test_baz),
56 {}
57 };
58
59 static struct kunit_suite example_test_suite = {
60 .name = "example",
61 .init = example_test_init,
62 .exit = example_test_exit,
63 .test_cases = example_test_cases,
64 };
65 kunit_test_suite(example_test_suite);
66
67 In the above example, the test suite ``example_test_suite``, runs the
68 test cases ``example_test_foo``, ``example_test_bar``, and
69 ``example_test_baz``. Before running the test, the ``example_test_init``
70 is called and after running the test, ``example_test_exit`` is called.
71 The ``kunit_test_suite(example_test_suite)`` registers the test suite
72 with the KUnit test framework.
73
74 Executor
75 --------
76
77 The KUnit executor can list and run built-in KUnit tests on boot.
78 The Test suites are stored in a linker section
79 called ``.kunit_test_suites``. For the code, see ``KUNIT_TABLE()`` macro
80 definition in
81 `include/asm-generic/vmlinux.lds.h <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/asm-generic/vmlinux.lds.h?h=v6.0#n950>`_.
82 The linker section consists of an array of pointers to
83 ``struct kunit_suite``, and is populated by the ``kunit_test_suites()``
84 macro. The KUnit executor iterates over the linker section array in order to
85 run all the tests that are compiled into the kernel.
86
87 .. kernel-figure:: kunit_suitememorydiagram.svg
88 :alt: KUnit Suite Memory
89
90 KUnit Suite Memory Diagram
91
92 On the kernel boot, the KUnit executor uses the start and end addresses
93 of this section to iterate over and run all tests. For the implementation of the
94 executor, see
95 `lib/kunit/executor.c <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/kunit/executor.c>`_.
96 When built as a module, the ``kunit_test_suites()`` macro defines a
97 ``module_init()`` function, which runs all the tests in the compilation
98 unit instead of utilizing the executor.
99
100 In KUnit tests, some error classes do not affect other tests
101 or parts of the kernel, each KUnit case executes in a separate thread
102 context. See the ``kunit_try_catch_run()`` function in
103 `lib/kunit/try-catch.c <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/kunit/try-catch.c?h=v5.15#n58>`_.
104
105 Assertion Macros
106 ----------------
107
108 KUnit tests verify state using expectations/assertions.
109 All expectations/assertions are formatted as:
110 ``KUNIT_{EXPECT|ASSERT}_<op>[_MSG](kunit, property[, message])``
111
112 - ``{EXPECT|ASSERT}`` determines whether the check is an assertion or an
113 expectation.
114 In the event of a failure, the testing flow differs as follows:
115
116 - For expectations, the test is marked as failed and the failure is logged.
117
118 - Failing assertions, on the other hand, result in the test case being
119 terminated immediately.
120
121 - Assertions call the function:
122 ``void __noreturn __kunit_abort(struct kunit *)``.
123
124 - ``__kunit_abort`` calls the function:
125 ``void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)``.
126
127 - ``kunit_try_catch_throw`` calls the function:
128 ``void kthread_complete_and_exit(struct completion *, long) __noreturn;``
129 and terminates the special thread context.
130
131 - ``<op>`` denotes a check with options: ``TRUE`` (supplied property
132 has the boolean value "true"), ``EQ`` (two supplied properties are
133 equal), ``NOT_ERR_OR_NULL`` (supplied pointer is not null and does not
134 contain an "err" value).
135
136 - ``[_MSG]`` prints a custom message on failure.
137
138 Test Result Reporting
139 ---------------------
140 KUnit prints the test results in KTAP format. KTAP is based on TAP14, see
141 Documentation/dev-tools/ktap.rst.
142 KTAP works with KUnit and Kselftest. The KUnit executor prints KTAP results to
143 dmesg, and debugfs (if configured).
144
145 Parameterized Tests
146 -------------------
147
148 Each KUnit parameterized test is associated with a collection of
149 parameters. The test is invoked multiple times, once for each parameter
150 value and the parameter is stored in the ``param_value`` field.
151 The test case includes a KUNIT_CASE_PARAM() macro that accepts a
152 generator function. The generator function is passed the previous parameter
153 and returns the next parameter. It also includes a macro for generating
154 array-based common-case generators.
155
156 kunit_tool (Command-line Test Harness)
157 ======================================
158
159 ``kunit_tool`` is a Python script, found in ``tools/testing/kunit/kunit.py``. It
160 is used to configure, build, execute, parse test results and run all of the
161 previous commands in correct order (i.e., configure, build, execute and parse).
162 You have two options for running KUnit tests: either build the kernel with KUnit
163 enabled and manually parse the results (see
164 Documentation/dev-tools/kunit/run_manual.rst) or use ``kunit_tool``
165 (see Documentation/dev-tools/kunit/run_wrapper.rst).
166
167 - ``configure`` command generates the kernel ``.config`` from a
168 ``.kunitconfig`` file (and any architecture-specific options).
169 The Python scripts available in ``qemu_configs`` folder
170 (for example, ``tools/testing/kunit/qemu configs/powerpc.py``) contains
171 additional configuration options for specific architectures.
172 It parses both the existing ``.config`` and the ``.kunitconfig`` files
173 to ensure that ``.config`` is a superset of ``.kunitconfig``.
174 If not, it will combine the two and run ``make olddefconfig`` to regenerate
175 the ``.config`` file. It then checks to see if ``.config`` has become a superset.
176 This verifies that all the Kconfig dependencies are correctly specified in the
177 file ``.kunitconfig``. The ``kunit_config.py`` script contains the code for parsing
178 Kconfigs. The code which runs ``make olddefconfig`` is part of the
179 ``kunit_kernel.py`` script. You can invoke this command through:
180 ``./tools/testing/kunit/kunit.py config`` and
181 generate a ``.config`` file.
182 - ``build`` runs ``make`` on the kernel tree with required options
183 (depends on the architecture and some options, for example: build_dir)
184 and reports any errors.
185 To build a KUnit kernel from the current ``.config``, you can use the
186 ``build`` argument: ``./tools/testing/kunit/kunit.py build``.
187 - ``exec`` command executes kernel results either directly (using
188 User-mode Linux configuration), or through an emulator such
189 as QEMU. It reads results from the log using standard
190 output (stdout), and passes them to ``parse`` to be parsed.
191 If you already have built a kernel with built-in KUnit tests,
192 you can run the kernel and display the test results with the ``exec``
193 argument: ``./tools/testing/kunit/kunit.py exec``.
194 - ``parse`` extracts the KTAP output from a kernel log, parses
195 the test results, and prints a summary. For failed tests, any
196 diagnostic output will be included.
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