Instruction file imported from display-protocol/dp1-publisher (.cursor/rules/35-testing-tdd.mdc). Copyright stays with the author.

Testing and Verification Rule

1) Required sequence

1. Isolate brittle logic where practical (pure helpers separate from JSX).
2. Add or extend automated tests when a runner exists and coverage adds real signal.
3. Keep production wiring cohesive (components → lib).
4. Run verification before handing off.

2) Constraints

• Do not ship behavior changes that break npm run build (tsc + bundle) unless explicitly approved.
• For meaningful feed integration or signing changes, smoke behavior against a reachable feed locally when feasible (DEVELOPMENT.md).
• Prefer explicit failure paths and user-visible diagnostics over silent mismatches (FeedAPIError).

3) Required verification

Run scripts/agent-helpers/post-implementation-checks from the repo root (requires node_modules — use npm ci or npm install).

This script matches CI intent: npm run lint and npm run build.

4) Coverage posture

Until Vitest/Jest lands, TypeScript correctness is exercised by npm run build.

When tests exist: prioritize src/lib helpers (URI validation, merge, signing inputs), error shaping, and small pure utilities over broad component snapshots.

Do not allow meaningful regressions in documented invariants without calling them out.