The best test for any ballast is a known good lamp. I don't mean a new lamp, I mean a known good one.
Make sure you have power to the ballast and put a lamp from another fixture that was working in the fixture in question. If it doesn't work you have a bad ballast.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof