Plugin coverage

Getting coverage on pytest plugins is a very particular situation. Because of how pytest implements plugins (using setuptools entrypoints) it doesn’t allow controlling the order in which the plugins load. See pytest/issues/935 for technical details.

The current way of dealing with this problem is using the append feature and manually starting pytest-cov’s engine, eg:

COV_CORE_SOURCE=src COV_CORE_CONFIG=.coveragerc COV_CORE_DATAFILE=.coverage.eager pytest --cov=src --cov-append

Alternatively you can have this in tox.ini (if you’re using Tox of course):

[testenv]
setenv =
    COV_CORE_SOURCE=
    COV_CORE_CONFIG={toxinidir}/.coveragerc
    COV_CORE_DATAFILE={toxinidir}/.coverage

And in pytest.ini / tox.ini / setup.cfg:

[tool:pytest]
addopts = --cov --cov-append