Release Notes

This page briefly summarizes the KUnit changes in each Linux release.

For more specific documentation on KUnit features, see the in-kernel documentation: https://kernel.org/doc/html/latest/dev-tools/kunit.

5.5

  • KUnit introduced, including all the basic functionality.

  • kunitconfig was renamed to .kunitconfig later in in 5.5 (commit)

5.6

  • KUnit tests can be built as modules, docs

5.7

  • kunit.py switched to using .kunit/ as the default build dir (and .kunitconfig => .kunit/.kunitconfig).

  • CONFIG_KUNIT_DEBUGFS to expose per-suite test results in /sys/kernel/debug/kunit/<suite>/results, docs

5.8

  • kunit.py now supports separate config/build/exec/parse commands in addition to run.

    • You can use these if you don’t want to let kunit.py run do everything for you, e.g. if you want to run manually but parse the results using kunit.py.

  • CONFIG_KUNIT_ALL_TESTS introduced

    • This is just a convention. New tests should use it like so:

config FOO_KUNIT_TEST
        tristate "KUnit test for foo" if !KUNIT_ALL_TESTS
        depends on KUNIT
        default KUNIT_ALL_TESTS
        help
          This builds unit tests for foo.

See the upstream documentation for the authoritative source on how to write Kconfig entries.

5.9

  • Named resources: tests can store and retrieve data via string keys.

    • This is a power feature intended to be a cleaner alternative to using global variables in tests.

    • See test_kasan.c for an example that uses "kasan_data".

5.10

  • KASAN violations cause the current KUnit test case to be marked FAILED.

    • Note: KASAN doesn’t currently work on UML.

5.11

  • Parameterized testing: see the docs.

5.12

  • You can pass in a path to a kunitconfig file instead of using .kunit/.kunitconfig, e.g.

$ ./tools/testing/kunit/kunit.py run --kunitconfig=fs/ext4/.kunitconfig

  • You can tell kunit.py to run a subset of built suites by passing in a glob argument, e.g.

# Only run "list" suites
$ ./tools/testing/kunit/kunit.py run '*list*'

5.13

  • Can call kunit_fail_current_test() from anywhere to fail the current KUnit test (e.g. if an invariant is broken, a UBSAN violation is detected, etc.)

  • You can pass a directory --kunitconfig and it’ll implicitly append .kunitconfig, e.g. kunit.py run --kunitconfig=lib/kunit.

5.14

  • kunit.py can run tests on non-UML architectures (using QEMU), docs

  • It’s now possible to generate code coverage reports when using UML, docs

  • Tests can call kunit_skip() to bail out and mark a test as “SKIPPED” instead of “PASSED” or “FAILED”

5.15

  • UBSAN violations cause the current KUnit test case to be marked FAILED.

  • Can pass kernel commandline parameters from kunit.py via --kernel_args

  • KUnit prints a summary per suite of how many test cases passed/failed to dmesg, e.g.

# property-entry: pass:7 fail:0 skip:0 total:7

5.16

  • You can filter on test names now in addition to suite names, e.g.

# Only run tests that contain "foo"
$ ./tools/testing/kunit/kunit.py run '*.*foo*'
# Only run tests in "mysuite" that contain "foo"
$ ./tools/testing/kunit/kunit.py run 'mysuite.*foo*'

  • You can ask kunit.py to run each suite/test by itself. This can be useful to track down issues due to non-hermetic tests

$ ./tools/testing/kunit/kunit.py run --run_isolated=suite
$ ./tools/testing/kunit/kunit.py run --run_isolated=test

  • kunit.py’s parsing logic was largely rewritten, so the output looks slightly different

    • Parsed output is also now mostly printed out in real time.

  • kunit.py with --raw_output will print output in real time.

  • In-kernel documentation has been significantly revamped.

5.17

  • Print out parsed test results in real time.

  • Allow tweaking Kconfig options from command-line, e.g.

$ ./tools/testing/kunit/kunit.py run --kconfig_add=MY_CONFIG=y

  • Reconfigure kunit kernel when the used kunitconfig has changed

    • Before, if you removed an entry from .kunitconfig, kunit.py would not reconfigure, so your edit would have no effect.

    • This now also works if you remove a --kconfig_add flag.

  • Print out parameters as sub-test cases (both in raw and parsed output), e.g.:

[12:37:14] =============== ext4_inode_test (1 subtest) ================
[12:37:14] ======= inode_test_xtimestamp_decoding (16 subtests) =======
[12:37:14] [PASSED] 1901-12-13 Lower bound of 32bit < 0 timestamp, no extra bits
...
[12:37:14] [PASSED] 2446-05-10 Upper bound of 32bit >=0 timestamp. All extra sec bits on
[12:37:14] ========= [PASSED] inode_test_xtimestamp_decoding ==========
[12:37:14] ================= [PASSED] ext4_inode_test =================
[12:37:14] ============================================================

5.18 (tentative)

  • Drastically decrease stack usage of KUNIT_EXPECT_ macros.

    • Before, we largely relied on the compiler to optimize away some internal structs, but that didn’t always work.

    • Now on UML (x86_64), KUNIT_EXPECT_EQ() uses 32 bytes instead of 88.