+1 Thanks, Alex On Mar 15, 2018 12:26, "Thomas Mortagne" <[email protected]> wrote: +1 On Thu, Mar 15, 2018 at 9:30 AM, Vincent Massol <[email protected]> wrote:

Hi devs,

As part of the STAMP research project, we’ve developed a new tool (Descartes, based on Pitest) to measure the quality of tests. It generates a mutation score for your tests, defining how good the tests are. Technical Descartes performs some extreme mutations on the code under test (e.g. remove content of void methods, return true for methods returning a boolean, etc - See https://github.com/STAMP-project/pitest-descartes). If the test continues to pass then it means it’s not killing the mutant and thus its mutation score decreases.

So in short: * Jacoco/Clover: measure how much of the code is tested * Pitest/Descartes: measure how good the tests are

Both provide a percentage value.

I’m proposing to compute the current mutation scores for xwiki-commons and xwiki-rendering and fail the build when new code is added that reduce the mutation score threshold (exactly the same as our jacoco threshold and strategy).

I consider this is an experiment to push the limit of software engineering a bit further. I don’t know how well it’ll work or not. I propose to do the work and test this for over 2-3 months and see how well it works or not. At that time we can then decide whether it works or not (i.e whether the gains it brings are more important than the problems it causes).

Here’s my +1 to try this out.

Some links: * pitest: http://pitest.org/ * descartes: https://github.com/STAMP-project/pitest-descartes * http://massol.myxwiki.org/xwiki/bin/view/Blog/ControllingTestQuality * http://massol.myxwiki.org/xwiki/bin/view/Blog/MutationTestingDescartes

If you’re curious, you can see a screenshot of a mutation score report at http://massol.myxwiki.org/xwiki/bin/download/Blog/MutationTestingDescartes/ report.png

Please cast your votes.

Thanks -Vincent

-- Thomas Mortagne