There's a fair amount of truth to this. Many applications are glorified SQL generators, that effectively JIT compile the application logic to SQL. So if you wan

There's a fair amount of truth to this. Many applications are glorified SQL generators, that effectively JIT compile the application logic to SQL. So if you want to test the application logic, then you need to run it on the runtime that it has been compiled for, that is: the database. Testing the application code in isolation would be like trying to test that your compiled binary contains the machine code instructions you expect, rather than testing that it actually runs correctly. There are niche times when that's useful, but most of the time, not really.