Ballast test on outdoor floodlight

I have 2 Lithonia 65 watt fluorescent outdoor floodlights. Up till yesterday both were working fine and then one failed to light. I pulled the lamp from the one that was not working and inserted it in the other working one and it lit up. So I know the bulb is fine. I tested the black power line coming in using a pen type tester an there was power . I tested for power at the ballast the same way and got a positive reading. The only thing I don't know how to test is the two pronged ballast which at this point I am assuming is where the failure is.

Would appreciate advice how to test the ballast.. I don't think I can replace it but want to eliminate all possible wiring problems before I buy a new floodlight.

Thanks.

 

A non contact tester is not accurate enough to tell you if you have real voltage. To determine that you need a multimeter, preferably analog, or a a neon test light, or a solenoid voltage tester.

 

should have mentioned I did test with multimeter and it indicated I had voltage on line. Really need info on how to test this type of ballast.