We'd only begin a dishwasher validation at my old job before I left, but I can give you some pointers:
The specifications will depend on your needs, and someone should give you guidance in that regard. What levels to they want to guarantee are no longer on the glassware? And for what products -- pharmaceuticals or the dishwashing soap, or water contaminants if they're using a tap water cycle?
The tests you'lll have to do will depend on what you're looking for. Say that you analyze a pharmaceutical by HPLC or GC. You'll have to determine the LOD for maybe the worst pharmaceutical, and verify that the dishwasher can remove it from glassware to a level that you can't detect it anymore. You can define "worst" as most toxic, or maybe easiest to detect. Detecting soap will be hard by UV detection, you may need to get a mass spec detector, or and ELSD, or go for ion chromatography.
Good luck.