How To Diagnose a Dead Microwave?

Anonymous asked 6 years ago
Microwave, GE Profile, Mod# JVM1790WK 01, Man# Sep 2009
The temp cut off switch wasn’t working # KSDI TSI 50/70, replaced it and it works.
However, I dismantled the microwave, tested each switch for continuity, the one mentioned above didn’t have continuity, located in the front on the base, so I removed it and jumped it with a wire and the microwave worked. Bought a new one, tested the new for continuity and it had no continuity, thought I just bought a bad switch but installed it anyway and the microwave worked. What happened?