Integration tests really are the best bang for the buck. So many times people think they tested their code by mocking something like the database layer and are

Integration tests really are the best bang for the buck. So many times people think they tested their code by mocking something like the database layer and are surprised when the application in production breaks. Everything can be tested in isolation and work perfectly, but often it's how the components work together that determines if the system works at all. Integration test what you can. Unit test core pieces of logic. Avoid mocks.