Re: [PATCH v2 00/17] kunit: introduce KUnit, the Linux kernel unit testing framework

Logan Gunthorpe
2019-05-09T23:41:23Z

On 2019-05-09 5:30 p.m., Theodore Ts'o wrote:
> On Thu, May 09, 2019 at 04:20:05PM -0600, Logan Gunthorpe wrote:
>>
>> The second item, arguably, does have significant overlap with kselftest.
>> Whether you are running short tests in a light weight UML environment or
>> higher level tests in an heavier VM the two could be using the same
>> framework for writing or defining in-kernel tests. It *may* also be valuable
>> for some people to be able to run all the UML tests in the heavy VM
>> environment along side other higher level tests.
>>
>> Looking at the selftests tree in the repo, we already have similar items to
>> what Kunit is adding as I described in point (2) above. kselftest_harness.h
>> contains macros like EXPECT_* and ASSERT_* with very similar intentions to
>> the new KUNIT_EXECPT_* and KUNIT_ASSERT_* macros.
>>
>> However, the number of users of this harness appears to be quite small. Most
>> of the code in the selftests tree seems to be a random mismash of scripts
>> and userspace code so it's not hard to see it as something completely
>> different from the new Kunit:
>>
>> $ git grep --files-with-matches kselftest_harness.h *
>
> To the extent that we can unify how tests are written, I agree that
> this would be a good thing. However, you should note that
> kselftest_harness.h is currently assums that it will be included in
> userspace programs. This is most obviously seen if you look closely
> at the functions defined in the header files which makes calls to
> fork(), abort() and fprintf().

Ah, yes. I obviously did not dig deep enough. Using kunit for in-kernel
tests and kselftest_harness for userspace tests seems like a sensible
line to draw to me. Trying to unify kernel and userspace here sounds
like it could be difficult so it's probably not worth forcing the issue
unless someone wants to do some really fancy work to get it done.

Based on some of the other commenters, I was under the impression that
kselftests had in-kernel tests but I'm not sure where or if they exist.
If they do exists, it seems like it would make sense to convert those to
kunit and have Kunit tests run-able in a VM or baremetal instance.

Logan