Do not improvise a door-switch test or defeat a sensor. The model may use a concealed magnetic sensor rather than an accessible mechanical button.
What the observation tells you
Holding a switch can change the light or fan state without proving that the alarm works correctly. It may also create a misleading account of what happens during normal use. A magnet taken from another household item is not a suitable diagnostic tool.
A useful next step
Use only an owner test described in the manual. Otherwise record the actual alarm behaviour during ordinary opening and closure, including any displayed symbol, and leave internal diagnosis to an engineer.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.