Reverse lights testing question

[JG1966]

Pardon my ignorance, but If I'm checking for current on the violet wire at the driver's side kick panel or at the tail light, does the engine need to be running with car in reverse or is ignition On with shifter in reverse good? Thanks.

 

[Darter6]

On with shifter in reverse

Missed the word Ignition. So Not running, ignition on, shifter in reverse.