This sort of things happens too often. Your problem made me look in-
line for an affordable cable tester. I regret that most are a few
hundreds of dollars.

I did find this one that is almost temptingly low enough to
get........... $46....

http://www.jdr.com/interact/item.asp?itemno=CT-RU

I think having a tester is still a good idea and will look for DIY
solutions to make a tester. Ringing the few lines in a cable should
be a simple enough matter to rig some sockets, led's, and a battery.

If anyone finds a $5 tester, Please let me know.