
Certainly all spaniels should have some health tests so should be listed for the poster to see under the health test result finder on the eh KC website.
So to OP please ask for the parents names and input those details into the tool to check they have been health tested. I would expect to see eye test result, Hip scores and also probably some DNA test results.
On the KC website you will be able to find which tests are required and recommended for the breed and only buy from breeders who at the very least do the required tests, but preferably the recommended ones too.
I would also expect a decent breeder to be a member of one or more breed clubs and actively involved with working and or showing their dogs, the breeding should be part of this interest not their prime involvement in their breed..