Depends on what you are trying to do. Your labels are missing the word "normally" which is a more common way to name them. A switch with a common, normally open (NO) and normally closed (NC), means the switch connects the common to the NC when the switch is not pressed (the "normal" position). When you press the switch the common gets connected to the NO (and disconnected from the NC). If the switch is bad, most anything could go wrong (connects NO to common all the time, connects NC to common all the time, completely open circuit, etc). A reliable way to test a switch is to disconnect at least the NC and NO wires and test the switch with an ohmmeter. With a simple on/off switch with 2 wires, a jumper between the wires will "turn on," but in your case, it is a little more complicated. If you trying to simulate pressing the switch, you would need to jumper NO (open) to common, but also REMOVE the connection to NC (closed).