linux-kernel - Re: [PATCH] lib: add basic KUnit test for lib/math

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Message-ID: <CAFd5g45o2G-bUvHNk2ehNuCsK6zVjN+rp88TyNmuJpfLbQi07g@mail.gmail.com>
Date:   Thu, 22 Oct 2020 11:53:50 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Daniel Latypov <dlatypov@...gle.com>,
        David Gow <davidgow@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] lib: add basic KUnit test for lib/math

On Thu, Oct 22, 2020 at 8:06 AM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Wed, Oct 21, 2020 at 10:47:50AM -0700, Daniel Latypov wrote:
> > On Tue, Oct 20, 2020 at 8:40 PM David Gow <davidgow@...gle.com> wrote:
> > > On Tue, Oct 20, 2020 at 6:46 AM Daniel Latypov <dlatypov@...gle.com> wrote:
> > > >
> > > > Add basic test coverage for files that don't require any config options:
> > > > * gcd.c
> > > > * lcm.c
> > > > * int_sqrt.c
> > > > * reciprocal_div.c
> > > > (Ignored int_pow.c since it's a simple textbook algorithm.)
> > > >
> > > I don't see a particular reason why int_pow.c being a simple algorithm
> > > means it shouldn't be tested. I'm not saying it has to be tested by
> > > this particular change -- and I doubt the test would be
> > > earth-shatteringly interesting -- but there's no real reason against
> > > testing it.
> >
> > Agreed on principle, but int_pow() feels like a special case.
> > I've written it the exact same way (modulo variable names+types)
> > several times in personal projects.
> > Even the spacing matched exactly in a few of those...
>
> But if you would like to *teach* somebody by this exemplary piece of code, you
> better do it close to ideal.
>
> > > > These tests aren't particularly interesting, but
> > > > * they're chosen as easy to understand examples of how to write tests
> > > > * provides a place to add tests for any new files in this dir
> > > > * written so adding new test cases to cover edge cases should be easy
> > >
> > > I think these tests can stand on their own merits, rather than just as
> > > examples (though I do think they do make good additional examples for
> > > how to test these sorts of functions).
> > > So, I'd treat this as an actual test of the maths functions (and
> > > you've got what seems to me a decent set of test cases for that,
> > > though there are a couple of comments below) first, and any use it
> > > gains as an example is sort-of secondary to that (anything that makes
> > > it a better example is likely to make it a better test anyway).
> > >
> > > In any case, modulo the comments below, this seems good to me.
> >
> > Ack.
> > I'll wait on Andy's input before deciding whether or not to push out a
> > v2 with the changes.
>
> You need to put detailed comments in the code to have it as real example how to
> create the KUnit test. But hey, it will mean that documentation sucks. So,
> please update documentation to cover issues that you found and which motivated
> you to create these test cases.

I don't entirely disagree; leaning too heavily on code examples can be
detrimental to docs. That being said, when I use other people's code,
I often don't even look at the docs. So, I think the ideal is to have
both.

> Summarize this, please create usable documentation first.