Sure. I wasn’t responding to your statements but I can understand what you mean. If your code manipulates the physical world (and not in a “sets this bit on a disk” sort of way) then you have to validate that action. Whether that valuation should be decoupled from the business logic that drives that piece really depends on the complexity of the system. At some point you are going to do full integration valuation so it’s a question of balance. How much is tested that way vs more isolated.

Tests that work and verify the system works are the Pri0 requirement. Most of the conversations about how best to test are structured for the benefit of people who are struggling with meeting the Pri0 because of maintainability. With enough effort any strategy can work.

> However in my domain we have lots of little data stores and nobody else needs access to that store.

If the little data stores are isolated to small individual areas of code then you probably already have the necessary isolation. Introducing the lightweight data store isolation layer might be useless (or not, context dependent). Now if these individual areas are doing things like handing off result sets to other code then I would have something different to say.