lawzava Test-First Implementation
Production code follows a failing test.
First inspect the entry point, callers, nearest convention, and coverage.
Use systematic-debugging for unknown causes.
Red, green, refactor
- Test real behavior at a stable observable boundary, rather than mock assertions.
- Verify red: confirm failure for the missing behavior, excluding setup errors and typos.
- Implement only what satisfies that test. Avoid speculative options, abstractions, and adjacent cleanup.
- Verify green: run the focused test, read its full result, and fix production code on failure.
- Refactor changed code while green. Repeat for the next behavior.
Understand dependencies before mocking. Do not add production APIs only for tests. Run the broader suite at task or milestone completion, before claiming success.
Code judgment
Repository instructions, existing code, and configured project tools are authoritative; skills supply defaults only where the repository is silent. Match local idioms, package boundaries, and public contracts unless they violate requirements or safety. Leave mechanical style to formatters, linters, and tests.
Before writing custom code, check existing code, the standard library, native platform features, and installed dependencies. Require behavioral fit; justify new dependencies by missing capability or maintenance benefit.
When simplifying changed code, preserve public contracts, trust-boundary validation, data-loss error handling, security, accessibility, and required tests. Do not sacrifice readability or correctness for line count. One caller or implementation does not make a boundary unnecessary.
For a deliberate simplification with a known limit, comment its ceiling and revisit condition using local conventions. Ordinary code needs no debt marker.
Type boundaries; validate untrusted data once at entry. Make error ownership explicit: expected, retryable, or terminal. Bound concurrent tasks with lifecycle, cancellation, failure policy, and resource limits. Model repeated domain state instead of synchronized booleans. Make retryable lifecycle operations idempotent. Move recurring failure invariants into types, tests, lint, or canonical helpers.
Load exactly one language reference when local code cannot settle a language-specific engineering decision:
- Go: references/go.md
- Python: references/python.md
- TypeScript: references/typescript.md
For generated output, prototypes destined for deletion, or prose-only configuration without executable behavior, use the nearest deterministic check. Never exempt product behavior. If a direct executable oracle beats a brittle characterization test, record the exception. Confirm the pre-change deficiency and run that oracle before and after the change.