Should be a small thin sqaure box on opposite side of engine of carb.
I do not know how to test it. They can be pricey if guessing that is the issue.
I would pull the shroud first and make sure a mouse didn't chew wire or leave a nest on top of sparkplug wire. Then, I would try that box.
The one below is for a motorcycle but looks similar to the mower module. The mower module/trigger might have 2 or 3 wires.