Date:   Tue, 16 Jun 2020 20:30:54 +0000
From:   "Bird, Tim" <Tim.Bird@...y.com>
To:     Brendan Higgins <brendanhiggins@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        David Gow <davidgow@...gle.com>
Subject: RE: RFC - kernel selftest result documentation (KTAP)



> -----Original Message-----
> From: Brendan Higgins
> 
> On Tue, Jun 16, 2020 at 9:42 AM Bird, Tim <Tim.Bird@...y.com> wrote:
> 
> Apologies for taking so long to get to this. I have been busy with
> some stuff internally at Google.
> 
> > > -----Original Message-----
> > > From: Paolo Bonzini <pbonzini@...hat.com>
> > >
> > > On 15/06/20 21:07, Bird, Tim wrote:
> > > >> Note: making the plan line required differs from TAP13 and TAP14. I
> > > >> think it's the right choice, but we should be clear.
> > >
> > > As an aside, where is TAP14?
> > By TAP14, I was referring to the current, undocumented, KUnit
> > conventions.
> 
> Not so. TAP14 is the proposed next version of TAP13:
> 
> https://github.com/TestAnything/testanything.github.io/pull/36
> https://github.com/isaacs/testanything.github.io/blob/tap14/tap-version-14-specification.md
> 

Thanks!  I thought there was a draft spec somewhere that hadn't been
pulled or approved or whatever.  I searched but couldn't find it.
Thanks for the links.

> Based on the discussion, it seems like most of the things we wanted
> from TAP14 would probably make it in if TAP ever accepts another pull
> request.
> 
> Our only real extension is how we print out a violated exception/assertion.

I guess I need to examine the TAP14 spec and see what it's got in it.
I didn't realize it had subtest nesting (it's been literally years since I
read it, and I didn't realize that KUnit was based on it).

> > > > With regards to making it optional or not, I don't have a strong
> > > > preference.  The extra info seems helpful in some circumstances.
> > > > I don't know if it's too onerous to make it a requirement or not.
> > > > I'd prefer if it was always there (either at the beginning or the end),
> > > > but if there is some situation where it's quite difficult to calculate,
> > > > then it would be best not to mandate it. I can't think of any impossible
> > > > situations at the moment.
> > >
> > > I think making the plan mandatory is a good idea.  "Late plans" work
> > > very well for cases where you cannot know in advance the number of tests
> > > (for example in filters that produce TAP from other output), and provide
> > > an additional safety net.
> > >
> > > >> "Bail out!" to be moved to "optional" elements, since it may not appear.
> > > >> And we should clarify TAP13 and TAP14's language to say it should only
> > > >> appear when the test is aborting without running later tests -- for this
> > > >> reason, I think the optional "description" following "Bail out!" should
> > > >> be made required. I.e. it must be: "Bail out! $reason"
> > > >
> > > > I'll make sure this is listed as optional.
> > > > I like adding a mandatory reason.
> > >
> > > +1.
> > >
> > > >> TAP13/14 makes description optional, are we making it required (I think
> > > >> we should). There seems to be a TAP13/14 "convention" of starting
> > > >> <description> with "- ", which I'm on the fence about it. It does make
> > > >> parsing maybe a little easier.
> > > >
> > > > I would like the description to be required.
> > > > I don't have a strong opinion on the dash.  I'm OK with either one (dash
> > > > or no dash), but we should make kselftest and KUnit consistent.
> > >
> > > I think no mandatory dash is better (or even mandatory no-dash!).  We
> > > can suggest removing it when formatting TAP output.
> >
> > My personal preference is to have the dash.  I think it's more human readable.
> > I note that the TAP spec has examples of result lines both with and without
> > the dash, so even the spec is ambiguous on this.   I think not mandating it
> > either way is probably best.  For regex parsers, it's easy to ignore with '[-]?'
> > outside the pattern groups that grab the number and description.
> 
> I don't think we care, because we don't use it.
OK.  If we decide to support both, it would be good to document that.

Thanks,
 -- Tim

> 
> > >
> > > >>> Finally, it is possible to use a test directive to indicate another
> > > >>> possible outcome for a test: that it was skipped.  To report that
> > > >>> a test case was skipped, the result line should start with the
> > > >>> result "not ok", and the directive "# SKIP" should be placed after
> > > >>> the test description. (Note that this deviates from the TAP13
> > > >>> specification).
> > >
> > > How so?  The description comes first, but there can be a description of
> > > the directive.
> > None of the examples of skips in the TAP13 spec have a test descriptions before
> > the '# SKIP' directive.  But maybe I read too much into the examples. There is a
> > format example, and a list of items in a result line that both have the test description
> > before the directive.  So maybe I read this wrong.
> >
> > >
> > >      not ok 4 - Summarized correctly # TODO Not written yet
> > >
> > > >>> It is usually helpful if a diagnostic message is emitted to explain
> > > >>> the reasons for the skip.  If the message is a single line and is
> > > >>> short, the diagnostic message may be placed after the '# SKIP'
> > > >>> directive on the same line as the test result.  However, if it is
> > > >>> not on the test result line, it should precede the test line (see
> > > >>> diagnostic data, next).
> > > >>>
> > > >>> Bail out!
> > > >>> ---------
> > > >>> If a line in the test output starts with 'Bail out!', it indicates
> > > >>> that the test was aborted for some reason.  It indicates that
> > > >>> the test is unable to proceed, and no additional tests will be
> > > >>> performed.
> > > >>>
> > > >>> This can be used at the very beginning of a test, or anywhere in the
> > > >>> middle of the test, to indicate that the test can not continue.
> > > >>
> > > >> I think the required syntax should be:
> > > >>
> > > >> Bail out! <reason>
> > > >>
> > > >> And to make it clear that this is optionally used to indicate an early
> > > >> abort. (Though with a leading plan line, a parser should be able to
> > > >> determine this on its own.)
> > >
> > > True.  However, "Bail out!" allow to distinguish issues with the harness
> > > (such as ENOSPC) from test aborts.
> > >
> > > >>>  - TODO directive
> > > >>
> > > >> Agreed: SKIP should cover everything TODO does.
> > >
> > > XFAIL/XPASS are different from SKIP.  I personally don't have a need for
> > > them, but kselftests includes XFAIL/XPASS exit codes and they aren't
> > > reflected into selftests/kselftest/runner.sh.
> > >
> > > Likewise, kselftest.h has ksft_inc_xfail_cnt but not
> > > ksft_test_result_xfail/ksft_test_result_xpass.
> > >
> > > It's important to notice in the spec that the TODO directive inverts the
> > > direction of ok/not-ok (i.e. XFAIL, the "good" result, is represented by
> > > "not ok # TODO").
> >
> > The TAP13 spec is not explicit about the result for TODO (and only provides
> > one example), but the text *does* say a TODO can represent a bug to be fixed.
> > This makes it the equivalent of XFAIL.  I hadn't noticed this before.  Thanks.
> >
> > >
> > > >>>  - test identifier
> > > >>>     - multiple parts, separated by ':'
> > > >>
> > > >> This is interesting... is the goal to be able to report test status over
> > > >> time by name?
> > >
> > > What about "/" instead?
> > In my experience, / is used in a lot of test descriptions (when quoting
> > file paths) (not in kselftest, but in lots of other tests).  Both Fuego
> > and KernelCI use colons, and that's what kselftest already uses,
> > so it seems like a good choice.
> >
> > >
> > > >>> Finally,
> > > >>>   - Should a SKIP result be 'ok' (TAP13 spec) or 'not ok' (current kselftest practice)?
> > > >>> See https://testanything.org/tap-version-13-specification.html
> > > >>
> > > >> Oh! I totally missed this. Uhm. I think "not ok" makes sense to me "it
> > > >> did not run successfully". ... but ... Uhhh ... how do XFAIL and SKIP
> > > >> relate? Neither SKIP nor XFAIL count toward failure, though, so both
> > > >> should be "ok"? I guess we should change it to "ok".
> > >
> > > See above for XFAIL.
> > >
> > > I initially raised the issue with "SKIP" because I have a lot of tests
> > > that depend on hardware availability---for example, a test that does not
> > > run on some processor kinds (e.g. on AMD, or old Intel)---and for those
> > > SKIP should be considered a success.
> > >
> > > Paolo
> > >
> > > > I have the same initial impression.  In my mind, a skip is "not ok", since
> > > > the test didn't run. However, a SKIP and should be treated differently
> > > > from either "ok" or "not ok" by the results interpreter, so I don't think it
> > > > matters.  Originally I was averse to changing the SKIP result to "ok"
> > > > (as suggested by Paulo Bonzini [1]), but I checked and it's pretty trivial to
> > > > change the parser in Fuego, and it would make the kernel results format
> > > > match the TAP13 spec.  I don't see a strong reason for us to be different
> > > > from TAP13 here.
> > > >
> > > > I raised this issue on our automated testing conference call last week
> > > > (which includes people from the CKI, Fuego, KernelCI and LKFT projects), and
> > > > so people should be chiming in if their parser will have a problem with this change.)
> > > >
> > > > [1]  https://lkml.kernel.org/lkml/20200610154447.15826-1-pbonzini@redhat.com/T/
> > > >
> > > > Thanks very much for the feedback.
> > > >  -- Tim
> > > >
> >

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