How can I test an RCA cable for signal or continuity

I ran a yellow RCA connector through my cargo trailer to hook up to my new stereo head unit. I tried to test it for the first time tonight and it didn't work. I had to splice the cable inside the trailer to be able to run it through. I suspect it might not be spliced right as there were two very small wires in the RCA cable. The yellow cable has a male connector on both ends but I have a gender changer. So, I am wondering how I can test the cable for continuity or signal. I have a voltmeter with tone testing on it.

 

Splice is likely the issue

 

I am guessing so and I think I might have the two wires reversed. I might take a battery and a couple leads to test for continuity between the center post and outer shield of the cable.