i set all of my strings on the 3 core connectors that ray sells, so that they are interchangale. I have one extra SSC not needed for my show set aside, as the test.
you load the test firmware on it, and then you can plug any string into it. you can set it up to run from a hub (in case you absolutely have to replace a running ssc with this one, or you can set it up to run from a cheap 10A 12v power supply from ray.
when your testing, you just make sure the other end is covered up to not short out.