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From:   Brendan Higgins <brendanhiggins@google.com>
Date:   Wed, 26 Jun 2019 15:16:36 -0700
Message-ID: <CAFd5g45PTtPumkpp1i41kkixZaR55pbqaF2DsuKNmh5UyAVwOg@mail.gmail.com>
Subject: Re: [PATCH v5 01/18] kunit: test: add KUnit test runner core
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     Frank Rowand <frowand.list@gmail.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Kees Cook <keescook@google.com>,
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On Tue, Jun 25, 2019 at 8:36 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
>
> On Tue, Jun 25, 2019 at 05:07:32PM -0700, Brendan Higgins wrote:
> > On Tue, Jun 25, 2019 at 3:33 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
> > >
> > > On Mon, Jun 17, 2019 at 01:25:56AM -0700, Brendan Higgins wrote:
> > > > +/**
> > > > + * module_test() - used to register a &struct kunit_module with KUnit.
> > > > + * @module: a statically allocated &struct kunit_module.
> > > > + *
> > > > + * Registers @module with the test framework. See &struct kunit_module for more
> > > > + * information.
> > > > + */
> > > > +#define module_test(module) \
> > > > +             static int module_kunit_init##module(void) \
> > > > +             { \
> > > > +                     return kunit_run_tests(&module); \
> > > > +             } \
> > > > +             late_initcall(module_kunit_init##module)
> > >
> > > Becuase late_initcall() is used, if these modules are built-in, this
> > > would preclude the ability to test things prior to this part of the
> > > kernel under UML or whatever architecture runs the tests. So, this
> > > limits the scope of testing. Small detail but the scope whould be
> > > documented.
> >
> > You aren't the first person to complain about this (and I am not sure
> > it is the first time you have complained about it). Anyway, I have
> > some follow on patches that will improve the late_initcall thing, and
> > people seemed okay with discussing the follow on patches as part of a
> > subsequent patchset after this gets merged.
> >
> > I will nevertheless document the restriction until then.
>
> To be clear, I am not complaining about it. I just find it simply
> critical to document its limitations, so folks don't try to invest
> time and energy on kunit right away for an early init test, if it
> cannot support it.
>
> If support for that requires some work, it may be worth mentioning
> as well.

Makes sense. And in anycase, it is something I do want to do, just not
right now. I will put a TODO here in the next revision.

> > > > +static void kunit_print_tap_version(void)
> > > > +{
> > > > +     if (!kunit_has_printed_tap_version) {
> > > > +             kunit_printk_emit(LOGLEVEL_INFO, "TAP version 14\n");
> > >
> > > What is this TAP thing? Why should we care what version it is on?
> > > Why are we printing this?
> >
> > It's part of the TAP specification[1]. Greg and Frank asked me to make
> > the intermediate format conform to TAP. Seems like something else I
> > should probable document...
>
> Yes thanks!
>
> > > > +             kunit_has_printed_tap_version = true;
> > > > +     }
> > > > +}
> > > > +
> > > > +static size_t kunit_test_cases_len(struct kunit_case *test_cases)
> > > > +{
> > > > +     struct kunit_case *test_case;
> > > > +     size_t len = 0;
> > > > +
> > > > +     for (test_case = test_cases; test_case->run_case; test_case++)
> > >
> > > If we make the last test case NULL, we'd just check for test_case here,
> > > and save ourselves an extra few bytes per test module. Any reason why
> > > the last test case cannot be NULL?
> >
> > Is there anyway to make that work with a statically defined array?
>
> No you're right.
>
> > Basically, I want to be able to do something like:
> >
> > static struct kunit_case example_test_cases[] = {
> >         KUNIT_CASE(example_simple_test),
> >         KUNIT_CASE(example_mock_test),
> >         {}
> > };
> >
> > FYI,
> > #define KUNIT_CASE(test_name) { .run_case = test_name, .name = #test_name }
>
> >
> > In order to do what you are proposing, I think I need an array of
> > pointers to test cases, which is not ideal.
>
> Yeah, you're right. The only other alternative is to have a:
>
> struct kunit_module {
>        const char name[256];
>        int (*init)(struct kunit *test);
>        void (*exit)(struct kunit *test);
>        struct kunit_case *test_cases;
> +       unsigned int num_cases;
> };
>
> And then something like:
>
> #define KUNIT_MODULE(name, init, exit, cases) { \
>         .name = name, \
>         .init = init, \
>         .exit = exit, \
>         .test_cases = cases,
>         num_cases = ARRAY_SIZE(cases), \
> }
>
> Let's evaluate which is better: one extra test case per all test cases, or
> an extra unsigned int for each kunit module.

I am in favor of the current method since init and exit are optional
arguments. I could see myself (actually I am planning on) adding more
optional things to the kunit_module, so having optional arguments will
make my life a lot easier since I won't have to go through big
refactorings around the kernel to support new features that tie in
here.