If you're looking to create a service, you will want to extensively research whichever breed(s) you're planning to provide health tests for and create an RNG, fair method of determining health issues/lack thereof for the dog.

Some people simply perform their own rolls on things such as genotype, hips, and elbows but it isn't backed up by a service and organizations are generally considered more 'reliable' from a RP standpoint. If your breed does not already have any offered health service, there's no shame in foregoing the testing until there is a service that covers the breed - in truth, people mostly use it to add variety and realism to creating breeding lines. It prevents every single dog on site from being 'breeding stock,' since it's unlikely in the real world that every puppy of every litter would go on to be healthy/quality for litters.