1 .. SPDX-License-Identifier: GPL-2.0
3 ============================
4 Tips For Running KUnit Tests
5 ============================
7 Using ``kunit.py run`` ("kunit tool")
8 =====================================
10 Running from any directory
11 --------------------------
13 It can be handy to create a bash function like:
17 function run_kunit() {
18 ( cd "$(git rev-parse --show-toplevel)" && ./tools/testing/kunit/kunit.py run $@ )
22 Early versions of ``kunit.py`` (before 5.6) didn't work unless run from
23 the kernel root, hence the use of a subshell and ``cd``.
25 Running a subset of tests
26 -------------------------
28 ``kunit.py run`` accepts an optional glob argument to filter tests. Currently
29 this only matches against suite names, but this may change in the future.
31 Say that we wanted to run the sysctl tests, we could do so via:
35 $ echo -e 'CONFIG_KUNIT=y\nCONFIG_KUNIT_ALL_TESTS=y' > .kunit/.kunitconfig
36 $ ./tools/testing/kunit/kunit.py run 'sysctl*'
38 We're paying the cost of building more tests than we need this way, but it's
39 easier than fiddling with ``.kunitconfig`` files or commenting out
42 However, if we wanted to define a set of tests in a less ad hoc way, the next
45 Defining a set of tests
46 -----------------------
48 ``kunit.py run`` (along with ``build``, and ``config``) supports a
49 ``--kunitconfig`` flag. So if you have a set of tests that you want to run on a
50 regular basis (especially if they have other dependencies), you can create a
51 specific ``.kunitconfig`` for them.
53 E.g. kunit has one for its tests:
57 $ ./tools/testing/kunit/kunit.py run --kunitconfig=lib/kunit/.kunitconfig
59 Alternatively, if you're following the convention of naming your
60 file ``.kunitconfig``, you can just pass in the dir, e.g.
64 $ ./tools/testing/kunit/kunit.py run --kunitconfig=lib/kunit
67 This is a relatively new feature (5.12+) so we don't have any
68 conventions yet about on what files should be checked in versus just
69 kept around locally. It's up to you and your maintainer to decide if a
70 config is useful enough to submit (and therefore have to maintain).
73 Having ``.kunitconfig`` fragments in a parent and child directory is
74 iffy. There's discussion about adding an "import" statement in these
75 files to make it possible to have a top-level config run tests from all
76 child directories. But that would mean ``.kunitconfig`` files are no
77 longer just simple .config fragments.
79 One alternative would be to have kunit tool recursively combine configs
80 automagically, but tests could theoretically depend on incompatible
81 options, so handling that would be tricky.
83 Setting kernel commandline parameters
84 -------------------------------------
86 You can use ``--kernel_args`` to pass arbitrary kernel arguments, e.g.
90 $ ./tools/testing/kunit/kunit.py run --kernel_args=param=42 --kernel_args=param2=false
93 Generating code coverage reports under UML
94 ------------------------------------------
97 TODO(brendanhiggins@google.com): There are various issues with UML and
98 versions of gcc 7 and up. You're likely to run into missing ``.gcda``
99 files or compile errors.
101 This is different from the "normal" way of getting coverage information that is
102 documented in Documentation/dev-tools/gcov.rst.
104 Instead of enabling ``CONFIG_GCOV_KERNEL=y``, we can set these options:
108 CONFIG_DEBUG_KERNEL=y
113 Putting it together into a copy-pastable sequence of commands:
117 # Append coverage options to the current config
118 $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
119 $ ./tools/testing/kunit/kunit.py run
120 # Extract the coverage information from the build dir (.kunit/)
121 $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/
123 # From here on, it's the same process as with CONFIG_GCOV_KERNEL=y
124 # E.g. can generate an HTML report in a tmp dir like so:
125 $ genhtml -o /tmp/coverage_html coverage.info
128 If your installed version of gcc doesn't work, you can tweak the steps:
132 $ ./tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6
133 $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/ --gcov-tool=/usr/bin/gcov-6
136 Running tests manually
137 ======================
139 Running tests without using ``kunit.py run`` is also an important use case.
140 Currently it's your only option if you want to test on architectures other than
143 As running the tests under UML is fairly straightforward (configure and compile
144 the kernel, run the ``./linux`` binary), this section will focus on testing
145 non-UML architectures.
148 Running built-in tests
149 ----------------------
151 When setting tests to ``=y``, the tests will run as part of boot and print
152 results to dmesg in TAP format. So you just need to add your tests to your
153 ``.config``, build and boot your kernel as normal.
155 So if we compiled our kernel with:
160 CONFIG_KUNIT_EXAMPLE_TEST=y
162 Then we'd see output like this in dmesg signaling the test ran and passed:
170 # example_simple_test: initializing
171 ok 1 - example_simple_test
174 Running tests as modules
175 ------------------------
177 Depending on the tests, you can build them as loadable modules.
179 For example, we'd change the config options from before to
184 CONFIG_KUNIT_EXAMPLE_TEST=m
186 Then after booting into our kernel, we can run the test via
190 $ modprobe kunit-example-test
192 This will then cause it to print TAP output to stdout.
195 The ``modprobe`` will *not* have a non-zero exit code if any test
196 failed (as of 5.13). But ``kunit.py parse`` would, see below.
199 You can set ``CONFIG_KUNIT=m`` as well, however, some features will not
200 work and thus some tests might break. Ideally tests would specify they
201 depend on ``KUNIT=y`` in their ``Kconfig``'s, but this is an edge case
202 most test authors won't think about.
203 As of 5.13, the only difference is that ``current->kunit_test`` will
206 Pretty-printing results
207 -----------------------
209 You can use ``kunit.py parse`` to parse dmesg for test output and print out
210 results in the same familiar format that ``kunit.py run`` does.
214 $ ./tools/testing/kunit/kunit.py parse /var/log/dmesg
217 Retrieving per suite results
218 ----------------------------
220 Regardless of how you're running your tests, you can enable
221 ``CONFIG_KUNIT_DEBUGFS`` to expose per-suite TAP-formatted results:
226 CONFIG_KUNIT_EXAMPLE_TEST=m
227 CONFIG_KUNIT_DEBUGFS=y
229 The results for each suite will be exposed under
230 ``/sys/kernel/debug/kunit/<suite>/results``.
231 So using our example config:
235 $ modprobe kunit-example-test > /dev/null
236 $ cat /sys/kernel/debug/kunit/example/results
239 # After removing the module, the corresponding files will go away
240 $ modprobe -r kunit-example-test
241 $ cat /sys/kernel/debug/kunit/example/results
242 /sys/kernel/debug/kunit/example/results: No such file or directory
244 Generating code coverage reports
245 --------------------------------
247 See Documentation/dev-tools/gcov.rst for details on how to do this.
249 The only vaguely KUnit-specific advice here is that you probably want to build
250 your tests as modules. That way you can isolate the coverage from tests from
251 other code executed during boot, e.g.
255 # Reset coverage counters before running the test.
256 $ echo 0 > /sys/kernel/debug/gcov/reset
257 $ modprobe kunit-example-test