That's a really good reason to write business logic in a way that doesn't have those dependencies hard wired in. I often end up in those sorts of nightmares in

That's a really good reason to write business logic in a way that doesn't have those dependencies hard wired in. I often end up in those sorts of nightmares in codebases that use the active record pattern (hiding database access everywhere), hooks, critical logic in the HTTP layer, and so on.