RE: Git Test Coverage Report (Tuesday, Sept 25)

["Jason Pyeron" <jpyeron@pdinc.us>]

> -----Original Message-----
> From: Derrick Stolee
> Sent: Wednesday, September 26, 2018 6:43 AM
> 
> On 9/25/2018 5:12 PM, Ben Peart wrote:
> >
> >
> > On 9/25/2018 2:42 PM, Derrick Stolee wrote:
> >> In an effort to ensure new code is reasonably covered by the test
> >> suite, we now have contrib/coverage-diff.sh to combine the gcov
> >> output from 'make coverage-test ; make coverage-report' with the
> >> output from 'git diff A B' to discover _new_ lines of code that are
> >> not covered.
> >>
<snip/>
> >
> > I looked at the lines that came from my patches and most if not all of
> > them are only going to be executed by the test suite if the correct
> > "special setup" option is enabled.  In my particular case, that is the
> > option "GIT_TEST_INDEX_THREADS=<n>" as documented in t/README.
> >
> > I suspect this will be the case for other code as well so I wonder if
> > the tests should be run with each the GIT_TEST_* options that exist to
> > exercise uncommon code paths with the test suite.  This should prevent
> > false positives on code paths that are actually covered by the test
> > suite as long as it is run with the appropriate option set.
> This is a bit tricky to do, but I will investigate. For some things, the
> values can conflict with each other (GIT_TEST_SPLIT_INDEX doesn't play
> nicely with other index options, I think). For others, we don't have the
> environment variables in all versions yet, as they are still merging down.

Remember that the code coverage is cumulative, on one of my projects where I have similar special cases the automated build will run through a sequence of different build options (including architectures) and executions - then generate the final report.

Another thought would be to weight the report for "new lines of code" - which is the same we do for our Fortify scans. We take the git blame for the change range and de-prioritize the findings for lines outside of the changed lines. This could give a tighter focus on the newly change code's test coverage.

> >
> > I realize it would take a long time to run the entire test suite with
> > all GIT_TEST_* variables so perhaps they can only be tested "as
> > needed" (ie when patches add new variables in the "special setups"
> > section of t/README).  This should reduce the number of combinations
> > that need to be run while still eliminating many of the false positive
> > hits.
> 
> This is something to think about. For my own thoughts, I was thinking of
> trying to run it when we see large blocks of code that are uncovered and
> obviously because of environment variables. This is what I was thinking
> when I saw your and Duy's commits in the output. I'll see if I can
> re-run the suite using GIT_TEST_INDEX_THREADS=2 and
> GIT_TEST_INDEX_VERSION=4.
> 
> Thanks,
> -Stolee