Rails Testing

Use for test-writing and test-review tasks. Patterns from Campfire and Fizzy test suites.

Defaults

• Minitest + fixtures. No RSpec, no FactoryBot.
• Test behavior, not implementation details.
• Keep tests deterministic and fast; parallelize(workers: :number_of_processors).
• Tests ship in the same commit/PR as the feature, not before, not later. Security fixes always include a regression test.
• Never add production complexity for testability (no test-induced design damage).

Coverage Budget (where 37signals actually spends)

• Heavy: model tests (domain invariants, concerns) and controller/integration tests (full request cycle, auth, formats).
• Light: a few system tests for the critical happy paths (one smoke test can cover signup→use); job tests only for jobs with real logic.
• None: view tests, JS/Stimulus unit tests, exhaustive channel tests. UI behavior is covered indirectly by system tests.
• Don't duplicate the same behavior assertion at multiple layers.

Fixtures

• Express relationships by label, not ID; use ERB for relative timestamps (created_at: <%= 1.hour.ago %>) and shared computed values (one bcrypt digest reused).
• Mirror app/models structure in test/models: app/models/card/closeable.rb ↔ test/models/card/closeable_test.rb; shared concerns under test/models/concerns/.
• UUID PKs break fixture ordering: generate deterministic, label-derived UUIDv7s in fixtures so .first/.last are stable and runtime records are always newer.
• Build rich-content fixtures with production code (ActionText::Attachment.from_attachable(user).to_html), not hand-written markup.

Good Practices