The warning raised is

../../path/plopp/widgets/debounce.py:23: in start
    self._task = asyncio.ensure_future(self._job())
../../../miniforge3/lib/python3.12/asyncio/tasks.py:693: in ensure_future
    loop = events.get_event_loop()

DeprecationWarning: There is no current event loop

This happens when running the unit tests on python 3.12.

I do not see the warning (even in the jupyter log console) when using the clipping planes in the notebook.
It could be a difference coming from the fact that the widget are never displayed when running the unit tests?

This makes a difference in some cases, for example the play widget does not function properly if it is not displayed in a notebook.