async def METHOD_NAME(widget, probe, event):
    handler = Mock()
    setattr(widget, f"on_{event}", handler)
    handler.assert_not_called()
    await getattr(probe, event)()
    handler.assert_called_once_with(widget)
    handler.reset_mock()
    setattr(widget, f"on_{event}", None)
    await getattr(probe, event)()
    handler.assert_not_called()