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

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Message-ID: <20201022191038.GO4077@smile.fi.intel.com>
Date:   Thu, 22 Oct 2020 22:10:38 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Daniel Latypov <dlatypov@...gle.com>
Cc:     David Gow <davidgow@...gle.com>,
        Brendan Higgins <brendanhiggins@...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 09:26:45AM -0700, Daniel Latypov wrote:
> 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:

...

> > 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,
> 
> Out of curiosity
> * By "it will mean that documentation sucks," do you mean that the
> documentation will rot faster if people are using the existing in-tree
> tests as their entrypoint?

Yes. And it will discourage to write documentation as well and read.
Good documentation is like a good book. I like how doc.python.org works for me
when I need something new to get about it, for example.

> * What level of detailed comments? On the level of kunit-example-test.c?
>   * More concretely, then we'd have a comment block linking to the

Something like explaining each line with KUNIT / kunit in it.
What it does and why it's written in the given form. Something like that.

> example and then describing table driven unit testing?
>   * And then maybe another block about invariants instead of the
> perhaps too-terse /* gcd(a,b) == gcd(b,a) */ ?

Right.

> > please update documentation to cover issues that you found and which motivated
> > you to create these test cases.
> >
> > Summarize this, please create usable documentation first.
> 
> Sounds good.
> I'm generally wary people not reading the docs, and of documentation
> examples becoming bitrotted faster than actual code.
> But so far KUnit seems to be doing relatively well on both fronts.

Dunno. As I told, I have created first unit test based on documentation (okay,
I looked at the code, but you may read this as ratio was 90% doc / 10% existing
code).

> usage.rst is currently the best place for this, but it felt like it
> would quickly become a dumping ground for miscellaneous tips and
> tricks.
> I'll spend some time thinking if we want a new file or not, based on
> how much I want to write about the things this test demonstrated
> (EXPECT_*MSG, table driven tests, testing invariants, etc).

Thanks!

> In offline discussions with David, the idea had come up with having a
> set of (relatively) simple tests in tree that the documentation could
> point to as examples of these things. That would keep the line count
> in usage.rst down a bit.
> (But then it would necessitate more tests like this math_test.c)

-- 
With Best Regards,
Andy Shevchenko