I saw the reply's from some people I respect on here and decided I needed to do more research. I'm always willing to listen and learn and I learned something new today.

Since 99.9% of my work is AC I needed to do some checking. Here's what I found was causing the difference of opinion.

Answer a DC test light is a tool with a normal open circuit that needs voltage to close to turn on light. So no it will not complete a circuit without voltage. Where an AC test light is just a closed circuit and will complete the circuit. ( yes I know it's a light bulb in a socket but that's all an ac test light is and i don't ever use them. I always use a meter).

The photo's show the ohm's and open circuit on the test tool.

I believe this source is still good info and would use a meter because almost ever car now has some draw (Clock,memory on radio & drivers ect.) that could turn the light on partially. Be sure and put the red lead in amp hole and set meter to DC amps. https://www.wikihow.com/Find-a-Parasitic-Battery-Drain