2007 MBP display/video issues. How to run test?

Do yo know of any software or websites that i can use to run disply/video/graphics test on my 2007 MBP to detect what exactly the issue is?? I was just watching a YouTube video when suddenly the video paused and I was getting a strobe effect. I then restored the computer and it was all boxy/pixelated/looked like an old nintendo game you had to blow into.