You obviously don't work with many control units of different purposes. What if, say your average enthusiast probes the injector plugs with a regular test light and does not get a pulse. He then decides to try and check the pins at the ecu itself. All it takes is a probe in the wrong pin to damage the ecu.
Bulb test lights should not be practiced to check anything related to ecu's of any sort. Thats what multimeters and led test lights are for.
Practice being safer than sorry. Thats all I'm trying to say here