Hi,
The black wire is the output, so yes, you can use a test light to ground. Also, the key will need to be in the start position for power to be sent. Also, you can confirm if there is power on the opposite wire as well. That one comes right from the ignition switch.
As far as a video, here is one that explains how to check a circuit using a test light. This will work for you as well.
https://youtu.be/Hlna_kUt7As
If you use a test light, provide a good ground to the ground wire in the light, and then probe the wire to check for power with the test light side of the tool.
Let me know if you have questions.
Take care,
Joe
Wednesday, December 8th, 2021 AT 7:54 PM