Most of my Python is web. Individual components, same as always - approach with a set API and not too many dependencies, and allow injection via some route if so. I also test web endpoints. One thing I really like is isolating tests that require data -- rather than mocking the database, for example, I'll create an in-memory SQLite DB used while running tests. That way I can test the full stack: a web API, see its results, and check what was changed in the database at the same time, all isolated from the 'real' stack.