[openstack-dev] [all][code quality] Voting coverage job (-1 if coverage get worse after patch)

Clint Byrum clint at fewbar.com
Mon Apr 20 16:59:53 UTC 2015

Excerpts from Boris Pavlovic's message of 2015-04-18 18:30:02 -0700:
> Hi stackers,
> Code coverage is one of the very important metric of overall code quality
> especially in case of Python. It's quite important to ensure that code is
> covered fully with well written unit tests.
> One of the nice thing is coverage job.
> In Rally we are running it against every check which allows us to get
> detailed information about
> coverage before merging patch:
> http://logs.openstack.org/84/175084/1/check/rally-coverage/c61d5e1/cover/
> This helped Rally core team to automate checking that new/changed code is
> covered by unit tests and we raised unit test coverage from ~78% to almost
> 91%.
> But it produces few issues:
> 1) >9k nitpicking - core reviewers have to put -1 if something is not
> covered by unit tests
> 2) core team scaling issues - core team members spend a lot of time just
> checking that whole code is covered by unit test and leaving messages like
> this should be covered by unit test
> 3) not friendly community - it's not nice to get on your code -1 from
> somebody that is asking just to write unit tests
> 4) coverage regressions - sometimes we accidentally accept patches that
> reduce coverage
> To resolve this issue I improved a bit coverage job in Rally project, and
> now it compares master vs master + patch coverage. If new coverage is less
> than master job is marked as -1.
> Here is the patch for job enhancement:
> https://review.openstack.org/#/c/174645/
> Here is coverage job in action:
> patch https://review.openstack.org/#/c/174677/
> job message
> http://logs.openstack.org/77/174677/4/check/rally-coverage/ba49c90/console.html#_2015-04-17_15_57_17_695

The link to the important line was key, because without it, just clicking
through from the review was incomprehensible to me. Can I suggest some
whitespace or bordering so we can see where the error is easily?

Anyway, interesting thoughts from everyone. I have to agree with those
that say this isn't reliable enough to make it vote. Non-voting would be
interesting though, if it gave a clear score difference, and a diff of
the two coverage reports. I think this is more useful as an automated
pointer to how things probably should be, but sometimes it's entirely
o-k to regress this number a few points.

Also graphing this over time in a post-commit job seems like a no-brainer.

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