[bluejekyll]

If you think of the DB like a service, then yes, people sometimes mock it. IMO, the danger comes when you start trying to mock things and act like a DB, i.e. you create some in-memory store to act like a DB. That's dangerous because then you're potentially introducing issues that are completely unrelated to the DB operations, and therefor not testing anything of value.

But it can be far cheaper to generate data through a mocked interface, than say fill a DB with data, and test against that data-set. Obviously there are ways to structure your code such that the DB isn't part of the data flow at all, but sometimes existing code structure isn't perfect.