Arduino mega 2560 r3 repair

Arduino mega quit displaying to my adafruit screen. I was using digital pin 9 with a fade sketch and was having issue. I went back to working on my display and I now have no display output. I've tryed all the different display sketchs that used to work. How can I tell if I might have fryed a circuit? Can I just Set the pins to high and check voltage or can I run a continuity test? Thanks for the help.