pytest-cov > 7.0.0 breaks coverage generation for notebooks only

[MarkusZimmerDLR]

Dear nbmake-folks,

Not sure whether this is a nbmake issue. However, since this only occurs when testing jupyther notebooks, with nbmake, I figured I put it here and might as well document it for others.
Normal testing with pytest and pytest-cov is unaffected.

Description

Running
pytest -v --nbmake --cov=somepackage somenotebook.ipynb

results in an error:

<...>lib/python3.13/site-packages/coverage/inorout.py:521: CoverageWarning: Module somepackage was never imported. (module-not-imported); see https://coverage.readthedocs.io/en/7.10.7/messages.html#warning-module-not-imported

Downgrading pytest-cov to < 7.0.0 resolves that error.

Package Versions

uv pip list | grep -E "nbmake|nbclient|ipykernel|pytest|pytest-cov|coverage|nbformat|pygments"

Using Python 3.13.7 environment at: <...>
accessible-pygments           0.0.5
coverage                      7.10.7
ipykernel                     6.30.1
ipython-pygments-lexers       1.1.1
jupyterlab-pygments           0.3.0
nbclient                      0.10.2
nbformat                      5.10.4
nbmake                        1.5.5
pygments                      2.19.2
pytest                        8.4.2
pytest-cov                    7.0.0

`.coveragerc` content:

[run]
relative_files = True

source =
  src/
  */site-packages/

omit =
    */test/*
    */doc/*
    */__internals/*
    */conda.recipe/*
    */.html
    */.txt


concurrency =
  thread
  #multiprocessing # leads to a plethora of issues an lower coverage

parallel = True
sigterm = True

[paths]
source =
  src/
  */site-packages/

[report]
omit =
    */test/*
    */doc/*
    */__internals/*
    */conda.recipe/*
    */*.html
    */*txt

Cheers,
Markus