both the switch and the cabling can be tested by running an end-to-end communications test -- a test that sends known data from one network device to another through the switch. for example, if you have two pcs on the network that have lan adapters between which you can run a link-level test or ping test through the switch, you can use this test to verify the entire communication path between the two pcs is functioning correctly. see your lan adapter documentation for more information on running a link test or ping test.