Why would you want to abstract away the underlying database?
Wouldn't it better to already use the target DB to cattch potential issues earlier? Also to avoid creating another layer of indirection, potentially complecting the codebase and reducing performance?
Primarily for libraries and deployment environments that aren't fully in your control which is still pretty common once you get to B2B interactions, SaaS is not something you can easily sell to certain environments. Depending on the assurance you need, you might even need to mock out the database entirely to test certain classes of database errors being recoverable or fail in a consistent state.
Even in SaaS systems, once you get large enough with a large enough test suite you'll be wanting to tier those tests starting with a lowest common denominator (sqlite) that doesn't incur network latency before getting into the serious integration tests.
