How to test a refrigerator light bulb — ensure it turns off when the door is closed?

To test whether the light bulb in the refrigerator turns off when the door is closed, you can use the following approach:

1. Visual observation: Open the refrigerator door and ensure the light bulb is on.
2. Close the door: Carefully close the door and check that the light bulb turns off.

For a more formal test, you can use a light sensor or photodetector that records the light level inside the refrigerator. When the door is open, the sensor should show a high light level; when closed, a low level.

If it is about software testing (for example, in a smart refrigerator), you can check the bulb status via an API or interface that returns the bulb status depending on the door state.

You can also verify the operation of the bulb's switch mechanism — usually a micro switch that activates when the door is closed.