This folder currently holds durations.json and blacklisted.json which are used in our pytest configuration. durations.json allows the two options --quickcheck and --veryquickcheck to be passed to pytest. Currently, the list of slow tests is updated intermittently by running:

$ ./.ci/generate_durations_log.sh
$ ./.ci/parse_durations_log.py
$ git commit -am "pytest: Updated .ci/durations.json"

make sure you have a C compiler, a Fortran compiler, numpy, scipy, cython, matplotlib & sage installed (the latter can be tricky, in which case just make sure that no sage tests are removed in the git diff).