https://www.destroyallsoftware.com/talks/boundaries
- test doubles
- test isolation example: Sweeper
- win: enables test-driven design
- win: outside-in tdd (top-down)
- win: fast tests
- lose: mocks and stubs may diverge from reality
https://www.destroyallsoftware.com/talks/boundaries
video: https://www.youtube.com/watch?v=WpkDN78P884