Mocking the database can be done, but only if you use the database as a generic storage layer. It's not trivial to keep the mocks updated in most applications.

Mocking the database can be done, but only if you use the database as a generic storage layer. It's not trivial to keep the mocks updated in most applications. Some ORMs and frameworks provide magic to do this, but as soon as you deviate from the framework it gets complex. You can build geospatial applications, time series, document, and full text search - iow leverage advanced features of Postgres extensions that most ORMs can't touch. Their behaviors can be complex and are part of the application, not simply a storage layer.