This repo exemplifies some broken behavior in the coverage module. Specifically, in python 3.8 (but not 3.7 or before), some break statements have no coverage as if they were never run, even if they very clearly were.

More information about this bug: https://github.com/nedbat/coveragepy/issues/772

With a virtualenv set up:

$ pip install -e .[test] $ tox

The frozen requirements of the broken state are also written in freeze_broken.txt, so it can also be installed with pip install -r freeze_broken.txt when in the coverage-bug folder.

pytest also reads from tox.ini so for a quick reproduction of 3.8 only you can simply install in a python3.8 virtualenv and run pytest.