@GuillaumeFavelier can you take a look and see if you agree that test_notebook.py is a better testing infrastructure than test.ipynb? To me it will be easier to add stuff this way, but it has the disadvantage that you can't directly run the notebook.

I'm fine not running in the notebook and updating test.ipynb directly is not convenient at all. I'll take a look and test locally

Similarly to #9190 (comment), the notebook tests were skipped so I pushed b08647c to fix that.

The tests are green for me locally and on Azure Notebook job:

...
mne/viz/_brain/tests/test_notebook.py::test_notebook_alignment[notebook] Coverage.py warning: --include is ignored because --source is set (include-ignored)
PASSED [ 17%]
mne/viz/_brain/tests/test_notebook.py::test_notebook_interactive[notebook] Coverage.py warning: --include is ignored because --source is set (include-ignored)
PASSED [ 17%]
mne/viz/_brain/tests/test_notebook.py::test_notebook_button_counts[notebook] Coverage.py warning: --include is ignored because --source is set (include-ignored)
PASSED [ 18%]
...

Is it still WIP? What is missing?

Is it still WIP? What is missing?

Ready for merge except tests still aren't passing on Windows:

c:\miniconda\lib\asyncio\events.py:501: in add_reader
    raise NotImplementedError
E   NotImplementedError

I think we probably just need to skip if the platform is Windows because it's probably not supported in some part of the stack. But I think we can rely on it working in practice for people. I'll push a commit to skip there

Feel free to rebase #9190 and incorporate tests there!