Improve pytest coverage report modules selection
pytest
discovers coverage options in all parent directories, so if run the tests from a
subdirectory of a Python project the sets --cov
we get spurious results in the
coverage reports. The option --cov-reset
cleans the list so that we correctly
select the modules we want to check.
See https://github.com/pytest-dev/pytest-cov/issues/460 for more details.