If your system has the ability to adjust the balance level, I would just do that and enjoy the music, after all, that is what the balance control is there for.And if no balance control, I have had success in different rooms by just moving one speaker in or out, in both cases by only an inch or two.
But if you want to make sure your equipment is functioning properly than I can understand.
If testing with equipment isn't practical, I would play a mono recording and listen to where the image is centered. Then I would swap cables down the chain to see if the image stayed in the same spot or moved left or right.