Language-Agnostic Testing Principles

Test-Driven Development (TDD)

Use this cycle for new or changed executable behavior and reproducible bug fixes. For a behavior-preserving refactor, first confirm existing tests pass or add passing characterization tests, then refactor and rerun the same regression evidence.

RED: confirm the new test fails for the intended reason. GREEN: implement the smallest passing change. REFACTOR: improve structure while the test remains green. VERIFY: run the repository's applicable regression checks.

Quality Requirements

• Treat coverage as a diagnostic signal for finding untested areas, not a target — a target gets gamed into trivial tests (Goodhart's Law)
• Concentrate tests on critical paths, business logic, and behavior whose regression would matter
• Prioritize meaningful assertions over the coverage number; any CI threshold is the project's config, not a quality goal in itself
• Use project-configured speed budgets when present. Otherwise investigate test speed only when observed feedback or CI cost is material to the current outcome; retain slower tests when their proof boundary requires it

Test Design Rules