Pragmatic testing tradeoffs recommended in Counterintuitive Rails pt. 2. Fixtures beat factories for speed, cross-references, and the ability to reload exploratory scenarios into the dev database. Stubs beat mocks because mocks verify call structure, turning black-box tests into white-box tests that break on any restructuring. RSpec's matcher ecosystem is overvalued; minitest plus power_assert gives enough expressivity without locking knowledge into a framework-specific DSL.