linux-kernel - Re: [PATCH v2] lib: Convert test

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Date:   Fri, 23 Oct 2020 19:13:00 +0530
From:   Arpitha Raghunandan <98.arpi@...il.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     brendanhiggins@...gle.com, skhan@...uxfoundation.org,
        pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, alexandre.belloni@...tlin.com,
        gregkh@...uxfoundation.org, rdunlap@...radead.org,
        idryomov@...il.com, kunit-dev@...glegroups.com,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH v2] lib: Convert test_printf.c to KUnit

On 23/10/20 4:36 pm, Rasmus Villemoes wrote:
> On 22/10/2020 21.16, Andy Shevchenko wrote:
>> On Thu, Oct 22, 2020 at 08:43:49PM +0530, Arpitha Raghunandan wrote:
>>> Convert test lib/test_printf.c to KUnit. More information about
>>> KUnit can be found at:
>>> https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html.
>>> KUnit provides a common framework for unit tests in the kernel.
>>> KUnit and kselftest are standardizing around KTAP, converting this
>>> test to KUnit makes this test output in KTAP which we are trying to
>>> make the standard test result format for the kernel. More about
>>> the KTAP format can be found at:
>>> https://lore.kernel.org/linux-kselftest/CY4PR13MB1175B804E31E502221BC8163FD830@CY4PR13MB1175.namprd13.prod.outlook.com/.
>>> I ran both the original and converted tests as is to produce the
>>> output for success of the test in the two cases. I also ran these
>>> tests with a small modification to show the difference in the output
>>> for failure of the test in both cases. The modification I made is:
>>> - test("127.000.000.001|127.0.0.1", "%pi4|%pI4", &sa.sin_addr, &sa.sin_addr);
>>> + test("127-000.000.001|127.0.0.1", "%pi4|%pI4", &sa.sin_addr, &sa.sin_addr);
>>>
>>> Original test success:
>>> [    0.591262] test_printf: loaded.
>>> [    0.591409] test_printf: all 388 tests passed
>>>
>>> Original test failure:
>>> [    0.619345] test_printf: loaded.
>>> [    0.619394] test_printf: vsnprintf(buf, 256, "%piS|%pIS", ...)
>>> wrote '127.000.000.001|127.0.0.1', expected
>>> '127-000.000.001|127.0.0.1'
>>> [    0.619395] test_printf: vsnprintf(buf, 25, "%piS|%pIS", ...) wrote
>>> '127.000.000.001|127.0.0.', expected '127-000.000.001|127.0.0.'
>>> [    0.619396] test_printf: kvasprintf(..., "%piS|%pIS", ...) returned
>>> '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1'
>>> [    0.619495] test_printf: failed 3 out of 388 tests
>>>
>>> Converted test success:
>>>     # Subtest: printf-kunit-test
>>>     1..1
>>>     ok 1 - selftest
>>> ok 1 - printf-kunit-test
>>>
>>> Converted test failure:
>>>     # Subtest: printf-kunit-test
>>>     1..1
>>>     # selftest: EXPECTATION FAILED at lib/printf_kunit.c:82
>>> vsnprintf(buf, 256, "%pi4|%pI4", ...) wrote
>>> '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1'
>>>     # selftest: EXPECTATION FAILED at lib/printf_kunit.c:82
>>> vsnprintf(buf, 5, "%pi4|%pI4", ...) wrote '127.', expected '127-'
>>>     # selftest: EXPECTATION FAILED at lib/printf_kunit.c:118
>>> kvasprintf(..., "%pi4|%pI4", ...) returned
>>> '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1'
>>>     not ok 1 - selftest
>>> not ok 1 - printf-kunit-test
>>
>> Not bad. Rasmus, what do you think?
> 
> Much better, but that '1..1' and reporting the entire test suite as 1
> single (failing or passing) test is (also) a regression. Look at the
> original
> 
>>> [    0.591409] test_printf: all 388 tests passed
> 
> or
> 
>>> [    0.619495] test_printf: failed 3 out of 388 tests
> 
> That's far more informative, and I'd prefer if the summary information
> (whether in the all-good case or some-failing) included something like
> this. In particular, I have at some point spotted that I failed to
> properly hook up a new test case (or perhaps failed to re-compile, or
> somehow still ran the old kernel binary, don't remember which it was) by
> noticing that the total number of tests hadn't increased. The new output
> would not help catch such PEBKACs.
> 
> Rasmus
> 

Splitting the test into multiple test cases in KUnit will display the number and name of tests that pass or fail. This will be similar to the lib/list-test.c test as can be seen here: https://elixir.bootlin.com/linux/latest/source/lib/list-test.c. I will work on this for the next version of this patch.