No don't use a test light. all a test light is good for is finding power. it will not tell you resistance of the circuit which, after deciphering your post, is what you seem to have a problem with. Get a DMM and use ohms law. and keep the trash talk for the dinner table.
P.S. I'm a real mechanic (opposed to a fake one?) and I don't even own a test light.
Power Probe > Test Light