[Linux-kernel-mentees] [PATCH v3] lib: Convert test_printf.c to KUnit

Rasmus Villemoes linux at rasmusvillemoes.dk
Wed Nov 4 08:18:08 UTC 2020


On 03/11/2020 17.11, Petr Mladek wrote:
> On Tue 2020-11-03 12:52:23, Greg KH wrote:
>> On Tue, Nov 03, 2020 at 01:33:53PM +0200, Andy Shevchenko wrote:
>>> On Tue, Nov 03, 2020 at 04:40:49PM +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:
>>>> [    0.540860] test_printf: loaded.
>>>> [    0.540863] test_printf: random seed = 0x5c46c33837bc0619
>>>> [    0.541022] test_printf: all 388 tests passed
>>>>
>>>> Original test failure:
>>>> [    0.537980] test_printf: loaded.
>>>> [    0.537983] test_printf: random seed = 0x1bc1efd881954afb
>>>> [    0.538029] test_printf: vsnprintf(buf, 256, "%pi4|%pI4", ...) wrote '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1'
>>>> [    0.538030] test_printf: kvasprintf(..., "%pi4|%pI4", ...) returned '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1'
>>>> [    0.538124] test_printf: failed 2 out of 388 tests
>>>> [    0.538125] test_printf: random seed used was 0x1bc1efd881954afb
>>>>
>>>> Converted test success:
>>>>     # Subtest: printf
>>>>     1..25
>>>>     ok 1 - test_basic
>>>>     ok 2 - test_number
>>>>     ok 3 - test_string
>>>>     ok 4 - plain
>>>>     ok 5 - null_pointer
>>>>     ok 6 - error_pointer
>>>>     ok 7 - invalid_pointer
>>>>     ok 8 - symbol_ptr
>>>>     ok 9 - kernel_ptr
>>>>     ok 10 - struct_resource
>>>>     ok 11 - addr
>>>>     ok 12 - escaped_str
>>>>     ok 13 - hex_string
>>>>     ok 14 - mac
>>>>     ok 15 - ip
>>>>     ok 16 - uuid
>>>>     ok 17 - dentry
>>>>     ok 18 - struct_va_format
>>>>     ok 19 - time_and_date
>>>>     ok 20 - struct_clk
>>>>     ok 21 - bitmap
>>>>     ok 22 - netdev_features
>>>>     ok 23 - flags
>>>>     ok 24 - errptr
>>>>     ok 25 - fwnode_pointer
>>>> ok 1 - printf
>>>>
>>>> Converted test failure:
>>>>     # Subtest: printf
>>>>     1..25
>>>>     ok 1 - test_basic
>>>>     ok 2 - test_number
>>>>     ok 3 - test_string
>>>>     ok 4 - plain
>>>>     ok 5 - null_pointer
>>>>     ok 6 - error_pointer
>>>>     ok 7 - invalid_pointer
>>>>     ok 8 - symbol_ptr
>>>>     ok 9 - kernel_ptr
>>>>     ok 10 - struct_resource
>>>>     ok 11 - addr
>>>>     ok 12 - escaped_str
>>>>     ok 13 - hex_string
>>>>     ok 14 - mac
>>>>     # ip: 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'
>>>>     # ip: EXPECTATION FAILED at lib/printf_kunit.c:124
>>>> kvasprintf(..., "%pi4|%pI4", ...) returned '127.000.000.001|127.0.0.1', expected '127-000.000.001|127.0.0.1'
>>>>     not ok 15 - ip
>>>>     ok 16 - uuid
>>>>     ok 17 - dentry
>>>>     ok 18 - struct_va_format
>>>>     ok 19 - time_and_date
>>>>     ok 20 - struct_clk
>>>>     ok 21 - bitmap
>>>>     ok 22 - netdev_features
>>>>     ok 23 - flags
>>>>     ok 24 - errptr
>>>>     ok 25 - fwnode_pointer
>>>> not ok 1 - printf
>>>
>>> Better, indeed.
>>>
>>> But can be this improved to have a cumulative statistics, like showing only
>>> number of total, succeeded, failed with details of the latter ones?
>>
>> Is that the proper test output format?  We have a standard...

Actually more like xkcd#927.

> 
> What is the standard, please?
> 
> The original module produced:
> 
> [   48.577739] test_printf: loaded.
> [   48.578046] test_printf: all 388 tests passed
> 
> It comes from KSTM_MODULE_LOADERS() macro that has been created
> by the commit eebf4dd452377921e3a26 ("kselftest: Add test module
> framework header"). 

That's a bit of a simplification. That code was clearly lifted directly
from the original test_printf.c code
(707cc7280f452a162c52bc240eae62568b9753c2). test_bitmap.c cloned
test_printf.c (including a "Test cases for printf facility" comment...).
Later both were converted to use the KSTM header.

As the one coming up with that originally, I certainly endorse its use
as a standard way of producing a final, free-form, summary, and I prefer
to keep that total tally (i.e. 388) being printed for the reasons I've
previously stated. [*]

That said, I have absolutely nothing against _also_ producing
machine-parsable TAP output. And the above looks to be a good compromise
between spitting out one TAP line for each of the 388 test cases (or
checks, or atoms, whatever the indiviual parts are to be called) and
treating all of test_printf.c as one single PASS/FAIL test.

[*] If I add some test cases to the time_and_date and run the kernel
under virtme, I want to see 388 becoming something else, so that I know
that I actually ran the code I just added and not some stale vmlinux -
maybe I only did "make lib/test_printf.o" and didn't recreate vmlinux,
maybe I did "make vmlinux" but failed to notice the build was broken. BTDT.

And those summary lines are even more important to keep given my
"deterministic random testing" series - the seed used _must_ be reported
(preferably also in the "all good" case, but certainly in the "some
failed" case).

Arpitha, thank you for taking that series into account. Is there some
way to keep the print of the total number of "atoms" as well as the
reporting of the random seed? Or should the "deterministic random
testing" be done in the context of KUNIT rather than KSTM? I'm really
not sure why we have both nor which one one is supposed to write
against. But I would prefer that the framework, whichever one, provides
a means to get a deterministic sequence of random numbers, so that I
won't have to eventually copy-paste the boilerplate to test_sort.c and
test_list_sort.c - it's also much nicer if all test modules have a
somewhat consistent interface in terms of the module parameters they accept.

Rasmus


More information about the Linux-kernel-mentees mailing list