Tests verify behavior through public interfaces, not implementation. Good tests survive refactors; bad tests break on rename.
See tests.md and mocking.md for examples.
Anti-pattern: horizontal slices
Don't write all tests then all code. One behavior: RED → GREEN → repeat.
Workflow
- Plan — read
CONTEXT.md/ADRs. Confirm interface changes and behaviors to test with user. - Tracer bullet — one test, one minimal implementation, passes.
- Loop — one test at a time; only code to pass current test; no speculation.
- Refactor — only when GREEN; see refactoring.md.
Per-cycle checklist
- Describes behavior, not implementation
- Uses public interface only
- Minimal code for this test