If you have a plug with exposed wires you could just plug it in, touch a multimeter set to continuity test, or resistance if it doesn't have that, to one of the solder points and it should show continuity (low resistance) with one of the wires coming from the plug, and the other contact should show continuity with the other wire. If you don't have a plug with wires free stick the test probe against the back of the jack and it should show continuity with one of the contacts and the side of the jack near the front should connect with the other.