To replace the oil sensor you must remove the single use bolts that hold the stiffening plate.

I think the oil level only is sampled while the engine is running so your test didn't do anything. I'm not sure how the sensor works but seeing as it's probably also the thermistor that measures the temp, possibly the thermistor is at the top and detects when it's not wetted by the oil. Some simple programming would be able to notice that oil temp is suddenly cooler than the coolant temp which makes no sense. Some parts sites may have a how to on determining if the part is broken like what Ω reading on which pins. Since my sensor isn't apparently working, I'm curious myself.