Antipattern: Premature Abstraction & Dependency Injection

The smell

• Constructors that take a repo:, clock:, mailer:, gateway: keyword for every collaborator
• Repository / gateway / port classes wrapping a single Active Record model 1:1
• Test setup full of instance_double(...) / class_double(...) for things Rails already mocks (mailers, jobs, time)
• Only one production implementation exists; the "second" implementation is always a test double

Why it hurts

• Costs are real: extra files, extra wiring, harder onboarding
• Benefits are imaginary — the second adapter never arrives
• Tests exercise the seam, not the behavior
• DHH/Manrubia: Rails is the abstraction layer. Don't build a second one to test it

The fix

• Use Active Record directly — fixtures + test DB cover the "mocking" need
• Use Rails test helpers — travel_to, assert_emails, perform_enqueued_jobs, freeze_time
• Real objects in tests (see mock-heavy-tests)
• Defer the abstraction until you genuinely have two implementations. YAGNI applies hardest in Rails