Say you bring your dog in because he's just not acting himself. You tell the vet to "do anything necessary" to find out what's wrong but do NOT sign any contracts/consent forms for cost and are not informed of any tests that are being run. So the vet runs a bunch of different tests and you come back the next day to pick up your dog and are faced with a surprising $800 vet bill.

Because the vet didn't inform you of any costs and nothing was signed, is this considered malpractice and/or negligence?
Are vets legally obligated to inform clients of the cost before running any tests/treatments? Is this a verbal or written contract?
If you were to sue, could you win? Why or why not?

Again, this is just out of curiosity.

Any information/opinions are appreciated