You can test a dryer outlet by using a multimeter. Insert the two test leads into the tester if they aren't already installed. Turn the tester power on and set the selector to AC volts. Now adjust the setting to the 240-volt setting or the next highest setting. Insert the test leads into the two top "hot" slots in the receptacle. These are the two slots that are tipped at a 45 degree angle. The voltage at this point should read between 220-240 volts. Now read the voltage between each of the two hot leads to the neutral slot. It is the straight slot below the two "hot" slots. The voltage here should read between 110-120 volts. If all of these connections check out, you have a fully functioning dryer outlet.