linux-kernel - Re: [PATCH] kunit: Fix result propagation for parameterised tests

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Date:   Sat, 12 Jun 2021 07:14:21 +0800
From:   David Gow <davidgow@...gle.com>
To:     Brendan Higgins <brendanhiggins@...gle.com>
Cc:     Arpitha Raghunandan <98.arpi@...il.com>,
        Marco Elver <elver@...gle.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kunit: Fix result propagation for parameterised tests

On Sat, Jun 12, 2021 at 4:26 AM Brendan Higgins
<brendanhiggins@...gle.com> wrote:
>
> On Thu, Jun 10, 2021 at 8:57 PM David Gow <davidgow@...gle.com> wrote:
> >
> > When one parameter of a parameterised test failed, its failure would be
> > propagated to the overall test, but not to the suite result (unless it
> > was the last parameter).
> >
> > This is because test_case->success was being reset to the test->success
> > result after each parameter was used, so a failing test's result would
> > be overwritten by a non-failing result. The overall test result was
> > handled in a third variable, test_result, but this was disacarded after
> > the status line was printed.
>
> nit: s/disacarded/discarded/g
>
> > Instead, just propagate the result after each parameter run.
> >
> > Signed-off-by: David Gow <davidgow@...gle.com>
> > Fixes: fadb08e7c750 ("kunit: Support for Parameterized Testing")
>
> I tried to reproduce the problem described and was unable to. Anyway,
> from the code it definitely looks like there is a bug like you
> describe. And it definitely looks like your change should fix it.

I was able to reproduce this again myself. Note that the kunit_tool
wrapper does its own result propagation which doesn't have a similar
bug, so you won't see the issue in its parsed results. (Using the
--raw_output flag does show it, though).

Here's the output from a patched UUID suite, which deliberately fails
the first parameter of the first two tests and passes the other
parameters and tests, which exhibits the issue:

TAP version 14
1..1
   # Subtest: uuid
   1..4
   # uuid_correct_be: ASSERTION FAILED at lib/test_uuid.c:57
   Expected uuid_parse(data->uuid, &be) == 0, but
       uuid_parse(data->uuid, &be) == -22

failed to parse 'c33fx4995-3701-450e-9fbf-206a2e98e576'
   # uuid_correct_be: not ok 1 - c33fx4995-3701-450e-9fbf-206a2e98e576
   # uuid_correct_be: ok 2 - 64b4371c-77c1-48f9-8221-29f054fc023b
   # uuid_correct_be: ok 3 - 0cb4ddff-a545-4401-9d06-688af53e7f84
   not ok 1 - uuid_correct_be
   # uuid_correct_le: ASSERTION FAILED at lib/test_uuid.c:46
   Expected guid_parse(data->uuid, &le) == 0, but
       guid_parse(data->uuid, &le) == -22

failed to parse 'c33fx4995-3701-450e-9fbf-206a2e98e576'
   # uuid_correct_le: not ok 1 - c33fx4995-3701-450e-9fbf-206a2e98e576
   # uuid_correct_le: ok 2 - 64b4371c-77c1-48f9-8221-29f054fc023b
   # uuid_correct_le: ok 3 - 0cb4ddff-a545-4401-9d06-688af53e7f84
   not ok 2 - uuid_correct_le
   # uuid_wrong_be: ok 1 - c33f4995-3701-450e-9fbf206a2e98e576
   # uuid_wrong_be: ok 2 - 64b4371c-77c1-48f9-8221-29f054XX023b
   # uuid_wrong_be: ok 3 - 0cb4ddff-a545-4401-9d06-688af53e
   ok 3 - uuid_wrong_be
   # uuid_wrong_le: ok 1 - c33f4995-3701-450e-9fbf206a2e98e576
   # uuid_wrong_le: ok 2 - 64b4371c-77c1-48f9-8221-29f054XX023b
   # uuid_wrong_le: ok 3 - 0cb4ddff-a545-4401-9d06-688af53e
   ok 4 - uuid_wrong_le
ok 1 - uuid


Note the "not ok 1 - uuid_correct_be" line, yet it ending in "ok 1 - uuid".

>
> Anyway, I tried testing your fix, but given I was unable to reproduce
> the failure, I am not super confident in my testing. Still,
>
> Reviewed-by: Brendan Higgins <brendanhiggins@...gle.com>