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 Generating code coverage reports under UML
84 ------------------------------------------
87 TODO(brendanhiggins@google.com): There are various issues with UML and
88 versions of gcc 7 and up. You're likely to run into missing ``.gcda``
89 files or compile errors.
91 This is different from the "normal" way of getting coverage information that is
92 documented in Documentation/dev-tools/gcov.rst.
94 Instead of enabling ``CONFIG_GCOV_KERNEL=y``, we can set these options:
103 Putting it together into a copy-pastable sequence of commands:
107 # Append coverage options to the current config
108 $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
109 $ ./tools/testing/kunit/kunit.py run
110 # Extract the coverage information from the build dir (.kunit/)
111 $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/
113 # From here on, it's the same process as with CONFIG_GCOV_KERNEL=y
114 # E.g. can generate an HTML report in a tmp dir like so:
115 $ genhtml -o /tmp/coverage_html coverage.info
118 If your installed version of gcc doesn't work, you can tweak the steps:
122 $ ./tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6
123 $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/ --gcov-tool=/usr/bin/gcov-6
126 Running tests manually
127 ======================
129 Running tests without using ``kunit.py run`` is also an important use case.
130 Currently it's your only option if you want to test on architectures other than
133 As running the tests under UML is fairly straightforward (configure and compile
134 the kernel, run the ``./linux`` binary), this section will focus on testing
135 non-UML architectures.
138 Running built-in tests
139 ----------------------
141 When setting tests to ``=y``, the tests will run as part of boot and print
142 results to dmesg in TAP format. So you just need to add your tests to your
143 ``.config``, build and boot your kernel as normal.
145 So if we compiled our kernel with:
150 CONFIG_KUNIT_EXAMPLE_TEST=y
152 Then we'd see output like this in dmesg signaling the test ran and passed:
160 # example_simple_test: initializing
161 ok 1 - example_simple_test
164 Running tests as modules
165 ------------------------
167 Depending on the tests, you can build them as loadable modules.
169 For example, we'd change the config options from before to
174 CONFIG_KUNIT_EXAMPLE_TEST=m
176 Then after booting into our kernel, we can run the test via
180 $ modprobe kunit-example-test
182 This will then cause it to print TAP output to stdout.
185 The ``modprobe`` will *not* have a non-zero exit code if any test
186 failed (as of 5.13). But ``kunit.py parse`` would, see below.
189 You can set ``CONFIG_KUNIT=m`` as well, however, some features will not
190 work and thus some tests might break. Ideally tests would specify they
191 depend on ``KUNIT=y`` in their ``Kconfig``'s, but this is an edge case
192 most test authors won't think about.
193 As of 5.13, the only difference is that ``current->kunit_test`` will
196 Pretty-printing results
197 -----------------------
199 You can use ``kunit.py parse`` to parse dmesg for test output and print out
200 results in the same familiar format that ``kunit.py run`` does.
204 $ ./tools/testing/kunit/kunit.py parse /var/log/dmesg
207 Retrieving per suite results
208 ----------------------------
210 Regardless of how you're running your tests, you can enable
211 ``CONFIG_KUNIT_DEBUGFS`` to expose per-suite TAP-formatted results:
216 CONFIG_KUNIT_EXAMPLE_TEST=m
217 CONFIG_KUNIT_DEBUGFS=y
219 The results for each suite will be exposed under
220 ``/sys/kernel/debug/kunit/<suite>/results``.
221 So using our example config:
225 $ modprobe kunit-example-test > /dev/null
226 $ cat /sys/kernel/debug/kunit/example/results
229 # After removing the module, the corresponding files will go away
230 $ modprobe -r kunit-example-test
231 $ cat /sys/kernel/debug/kunit/example/results
232 /sys/kernel/debug/kunit/example/results: No such file or directory
234 Generating code coverage reports
235 --------------------------------
237 See Documentation/dev-tools/gcov.rst for details on how to do this.
239 The only vaguely KUnit-specific advice here is that you probably want to build
240 your tests as modules. That way you can isolate the coverage from tests from
241 other code executed during boot, e.g.
245 # Reset coverage counters before running the test.
246 $ echo 0 > /sys/kernel/debug/gcov/reset
247 $ modprobe kunit-example-test