Re: [PATCH v2] lib: Convert test_printf.c to KUnit

[Rasmus Villemoes]

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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/.
>> 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