The best way to determine if a light socket is working is to test its voltage with a multimeter. These are inexpensive devices that have a pair of probes. The probes are connected to an electrical device to test for a current. The voltage is displayed on the read-out.
Insert the plug for the black cord into the socket marked "COM" or "COMMON" on the mulitmeter.
Attach the plug for the red cord into the hole marked "V" and "mA" separated by the Greek letter omega.
Switch the multimeter dial so it points to "V" or "Volts." If your multimeter has several voltage options, choose "220V." These numbers indicate the highest voltage the multimeter will read, and 220 volts is the voltage of most household light sockets.
Remove the light bulb from the socket, and turn the light switch on.
Touch the tip of one of the two probes to the center of the socket on the brass plate.
Place the other probe against the inner wall of the light socket.
Look at the display on the multimeter for the voltage of the light socket.