I called asking for a list of "congenital" disorders for a border collie and was told there was no way to tell until I bought the insurance, my dog got sick and I turned in the claim for their review.
I asked about "hereditary" diseases for a dog of unknown parentage (I adopted a border collie rescue dog). They said the same applies: buy the insurance, wait for your dog to get sick, and we may or may not pay the claim. I decided not to buy the insurance. I found the same disclaimer on all the other policies out there.
I suggest putting money away in a savings account every month and call it your pet emergency fund. Hopefully you won't need it, but you can then decide how much to pay yourself back per incident.