Yeah, I think in that case, just make a decision as to whether or not you're going to use Pool or Conn in your application code. If you change your mind, just refactor; it's not worth maintaining the interface just to open up the opportunity to change in the future. Pool is probably the right choice forever.

If it's for testing, I'd just skip mocking that out and run the queries against the real database, like you do in the article. Production is going to connect to Postgres and run `select * from foobars`. Might as well run `select * from foobars` in the tests, so I'm not surprised when it doesn't work in production.