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Subject: Re: [PATCH v4 1/2] kunit: Support for Parameterized Testing
To:     Marco Elver <elver@google.com>
Cc:     Brendan Higgins <brendanhiggins@google.com>,
        skhan@linuxfoundation.org, Iurii Zaikin <yzaikin@google.com>,
        Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        KUnit Development <kunit-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-ext4@vger.kernel.org
References: <20201027174630.85213-1-98.arpi@gmail.com>
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 <73c4e46c-10f1-9362-b4fb-94ea9d74e9b2@gmail.com>
 <CANpmjNPxqQM0_f14ZwV3rHZzwhCtqx2fbOhHmXmiJawou6=z6Q@mail.gmail.com>
From:   Arpitha Raghunandan <98.arpi@gmail.com>
Message-ID: <77d6dc66-1086-a9ae-ccbc-bb062ff81437@gmail.com>
Date:   Thu, 5 Nov 2020 20:00:25 +0530
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On 05/11/20 2:00 pm, Marco Elver wrote:
> On Thu, 5 Nov 2020 at 08:32, Arpitha Raghunandan <98.arpi@gmail.com> wrote:
>>
>> On 28/10/20 12:51 am, Marco Elver wrote:
>>> On Tue, 27 Oct 2020 at 18:47, Arpitha Raghunandan <98.arpi@gmail.com> wrote:
>>>>
>>>> Implementation of support for parameterized testing in KUnit.
>>>> This approach requires the creation of a test case using the
>>>> KUNIT_CASE_PARAM macro that accepts a generator function as input.
>>>> This generator function should return the next parameter given the
>>>> previous parameter in parameterized tests. It also provides
>>>> a macro to generate common-case generators.
>>>>
>>>> Signed-off-by: Arpitha Raghunandan <98.arpi@gmail.com>
>>>> Co-developed-by: Marco Elver <elver@google.com>
>>>> Signed-off-by: Marco Elver <elver@google.com>
>>>> ---
>>>> Changes v3->v4:
>>>> - Rename kunit variables
>>>> - Rename generator function helper macro
>>>> - Add documentation for generator approach
>>>> - Display test case name in case of failure along with param index
>>>> Changes v2->v3:
>>>> - Modifictaion of generator macro and method
>>>> Changes v1->v2:
>>>> - Use of a generator method to access test case parameters
>>>>
>>>>  include/kunit/test.h | 34 ++++++++++++++++++++++++++++++++++
>>>>  lib/kunit/test.c     | 21 ++++++++++++++++++++-
>>>>  2 files changed, 54 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/kunit/test.h b/include/kunit/test.h
>>>> index 9197da792336..ec2307ee9bb0 100644
>>>> --- a/include/kunit/test.h
>>>> +++ b/include/kunit/test.h
>>>> @@ -107,6 +107,13 @@ struct kunit;
>>>>   *
>>>>   * @run_case: the function representing the actual test case.
>>>>   * @name:     the name of the test case.
>>>> + * @generate_params: the generator function for parameterized tests.
>>>> + *
>>>> + * The generator function is used to lazily generate a series of
>>>> + * arbitrarily typed values that fit into a void*. The argument @prev
>>>> + * is the previously returned value, which should be used to derive the
>>>> + * next value; @prev is set to NULL on the initial generator call.
>>>> + * When no more values are available, the generator must return NULL.
>>>>   *
>>>
>>> Hmm, should this really be the first paragraph? I think it should be
>>> the paragraph before "Example:" maybe. But then that paragraph should
>>> refer to generate_params e.g. "The generator function @generate_params
>>> is used to ........".
>>>
>>> The other option you have is to move this paragraph to the kernel-doc
>>> comment for KUNIT_CASE_PARAM, which seems to be missing a kernel-doc
>>> comment.
>>>
>>>>   * A test case is a function with the signature,
>>>>   * ``void (*)(struct kunit *)``
>>>> @@ -141,6 +148,7 @@ struct kunit;
>>>>  struct kunit_case {
>>>>         void (*run_case)(struct kunit *test);
>>>>         const char *name;
>>>> +       void* (*generate_params)(void *prev);
>>>>
>>>>         /* private: internal use only. */
>>>>         bool success;
>>>> @@ -162,6 +170,9 @@ static inline char *kunit_status_to_string(bool status)
>>>>   * &struct kunit_case for an example on how to use it.
>>>>   */
>>>>  #define KUNIT_CASE(test_name) { .run_case = test_name, .name = #test_name }
>>>
>>> I.e. create a new kernel-doc comment for KUNIT_CASE_PARAM here, and
>>> simply move the paragraph describing the generator protocol into that
>>> comment.
>>>
>>>> +#define KUNIT_CASE_PARAM(test_name, gen_params)                        \
>>>> +               { .run_case = test_name, .name = #test_name,    \
>>>> +                 .generate_params = gen_params }
>>>>
>>>>  /**
>>>>   * struct kunit_suite - describes a related collection of &struct kunit_case
>>>> @@ -208,6 +219,15 @@ struct kunit {
>>>>         const char *name; /* Read only after initialization! */
>>>>         char *log; /* Points at case log after initialization */
>>>>         struct kunit_try_catch try_catch;
>>>> +       /* param_value points to test case parameters in parameterized tests */
>>>
>>> Hmm, not quite: param_value is the current parameter value for a test
>>> case. Most likely it's a pointer, but it doesn't need to be.
>>>
>>>> +       void *param_value;
>>>> +       /*
>>>> +        * param_index stores the index of the parameter in
>>>> +        * parameterized tests. param_index + 1 is printed
>>>> +        * to indicate the parameter that causes the test
>>>> +        * to fail in case of test failure.
>>>> +        */
>>>
>>> I think this comment needs to be reformatted, because you can use at
>>> the very least use 80 cols per line. (If you use vim, visual select
>>> and do 'gq'.)
>>>
>>>> +       int param_index;
>>>>         /*
>>>>          * success starts as true, and may only be set to false during a
>>>>          * test case; thus, it is safe to update this across multiple
>>>> @@ -1742,4 +1762,18 @@ do {                                                                            \
>>>>                                                 fmt,                           \
>>>>                                                 ##__VA_ARGS__)
>>>>
>>>> +/**
>>>> + * KUNIT_ARRAY_PARAM() - Helper method for test parameter generators
>>>> + *                      required in parameterized tests.
>>>> + * @name:  prefix of the name for the test parameter generator function.
>>>> + *        It will be suffixed by "_gen_params".
>>>> + * @array: a user-supplied pointer to an array of test parameters.
>>>> + */
>>>> +#define KUNIT_ARRAY_PARAM(name, array)                                                         \
>>>> +       static void *name##_gen_params(void *prev)                                              \
>>>> +       {                                                                                       \
>>>> +               typeof((array)[0]) * __next = prev ? ((typeof(__next)) prev) + 1 : (array);     \
>>>> +               return __next - (array) < ARRAY_SIZE((array)) ? __next : NULL;                  \
>>>> +       }
>>>> +
>>>>  #endif /* _KUNIT_TEST_H */
>>>> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
>>>> index 750704abe89a..8ad908b61494 100644
>>>> --- a/lib/kunit/test.c
>>>> +++ b/lib/kunit/test.c
>>>> @@ -127,6 +127,12 @@ unsigned int kunit_test_case_num(struct kunit_suite *suite,
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(kunit_test_case_num);
>>>>
>>>> +static void kunit_print_failed_param(struct kunit *test)
>>>> +{
>>>> +       kunit_err(test, "\n\tTest failed at:\n\ttest case: %s\n\tparameter: %d\n",
>>>> +                                               test->name, test->param_index + 1);
>>>> +}
>>>
>>> Hmm, perhaps I wasn't clear, but I think I also misunderstood how the
>>> test case successes are presented: they are not, and it's all bunched
>>> into a single test case.
>>>
>>> Firstly, kunit_err() already prints the test name, so if we want
>>> something like "  # : the_test_case_name: failed at parameter #X",
>>> simply having
>>>
>>>     kunit_err(test, "failed at parameter #%d\n", test->param_index + 1)
>>>
>>> would be what you want.
>>>
>>> But I think I missed that parameters do not actually produce a set of
>>> test cases (sorry for noticing late). I think in their current form,
>>> the parameterized tests would not be useful for my tests, because each
>>> of my tests have test cases that have specific init and exit
>>> functions. For each parameter, these would also need to run.
>>>
>>> Ideally, each parameter produces its own independent test case
>>> "test_case#param_index". That way, CI systems will also be able to
>>> logically separate different test case params, simply because each
>>> param produced its own distinct test case.
>>>
>>> So, for example, we would get a series of test cases from something
>>> like KUNIT_CASE_PARAM(test_case, foo_gen_params), and in the output
>>> we'd see:
>>>
>>>     ok X - test_case#1
>>>     ok X - test_case#2
>>>     ok X - test_case#3
>>>     ok X - test_case#4
>>>     ....
>>>
>>> Would that make more sense?
>>>
>>> That way we'd ensure that test-case specific initialization and
>>> cleanup done in init and exit functions is properly taken care of, and
>>> you wouldn't need kunit_print_failed_param().
>>>
>>> AFAIK, for what I propose you'd have to modify kunit_print_ok_not_ok()
>>> (show param_index if parameterized test) and probably
>>> kunit_run_case_catch_errors() (generate params and set
>>> test->param_value and param_index).
>>>
>>> Was there a reason why each param cannot be a distinct test case? If
>>> not, I think this would be more useful.
>>>
>>
>> I tried adding support to run each parameter as a distinct test case by
>> making changes to kunit_run_case_catch_errors(). The issue here is that
>> since the results are displayed in KTAP format, this change will result in
>> each parameter being considered a subtest of another subtest (test case
>> in KUnit).
> 
> Do you have example output? That might help understand what's going on.
> 

The change that I tried can be seen here (based on the v4 patch):
https://gist.github.com/arpi-r/4822899087ca4cc34572ed9e45cc5fee.

Using the kunit tool, I get this error:

[19:20:41] [ERROR]  expected 7 test suites, but got -1
[ERROR] no tests run!
[19:20:41] ============================================================
[19:20:41] Testing complete. 0 tests run. 0 failed. 0 crashed.

But this error is only because of how the tool displays the results.
The test actually does run, as can be seen in the dmesg output:

TAP version 14
1..7
    # Subtest: ext4_inode_test
    1..1
    ok 1 - inode_test_xtimestamp_decoding 1
    ok 1 - inode_test_xtimestamp_decoding 2
    ok 1 - inode_test_xtimestamp_decoding 3
    ok 1 - inode_test_xtimestamp_decoding 4
    ok 1 - inode_test_xtimestamp_decoding 5
    ok 1 - inode_test_xtimestamp_decoding 6
    ok 1 - inode_test_xtimestamp_decoding 7
    ok 1 - inode_test_xtimestamp_decoding 8
    ok 1 - inode_test_xtimestamp_decoding 9
    ok 1 - inode_test_xtimestamp_decoding 10
    ok 1 - inode_test_xtimestamp_decoding 11
    ok 1 - inode_test_xtimestamp_decoding 12
    ok 1 - inode_test_xtimestamp_decoding 13
    ok 1 - inode_test_xtimestamp_decoding 14
    ok 1 - inode_test_xtimestamp_decoding 15
    ok 1 - inode_test_xtimestamp_decoding 16
ok 1 - ext4_inode_test
(followed by other kunit test outputs)

>> To make this work, a lot of changes in other parts will be required,
>> and it will get complicated. Running all parameters as one test case seems
>> to be a better option right now. So for now, I will modify what is displayed
>> by kunit_err() in case of test failure.
>>
>>>>  static void kunit_print_string_stream(struct kunit *test,
>>>>                                       struct string_stream *stream)
>>>>  {
>>>> @@ -168,6 +174,8 @@ static void kunit_fail(struct kunit *test, struct kunit_assert *assert)
>>>>         assert->format(assert, stream);
>>>>
>>>>         kunit_print_string_stream(test, stream);
>>>> +       if (test->param_value)
>>>> +               kunit_print_failed_param(test);
>>>>
>>>>         WARN_ON(string_stream_destroy(stream));
>>>>  }
>>>> @@ -239,7 +247,18 @@ static void kunit_run_case_internal(struct kunit *test,
>>>>                 }
>>>>         }
>>>>
>>>> -       test_case->run_case(test);
>>>> +       if (!test_case->generate_params) {
>>>> +               test_case->run_case(test);
>>>> +       } else {
>>>> +               test->param_value = test_case->generate_params(NULL);
>>>> +               test->param_index = 0;
>>>> +
>>>> +               while (test->param_value) {
>>>> +                       test_case->run_case(test);
>>>> +                       test->param_value = test_case->generate_params(test->param_value);
>>>> +                       test->param_index++;
>>>> +               }
>>>> +       }
>>>
>>> Thanks,
>>> -- Marco
>>>
>>
>> --
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