Testing Checklist

Testing Checklist

Tests are the executable spec. Optimize them for reading and for meaningful assertions, not for coverage numbers.

What to test

• Branch logic, boundaries, contracts, and error paths first.
• Skip trivial pass-throughs, framework internals, and implementation details.
• Test through the public surface, not private state or call order.

TDD loop (new behavior)

1. Agree the seam where the test attaches before writing it.
2. Red: write one failing test for the next thin slice; watch it fail for the intended reason.
3. Green: write the least code that makes it pass.
4. Refactor as a separate step, with the test green as the safety net.

Slice vertically (one thin path through every layer), not horizontally. One slice at a time.

Bug-fix protocol

1. Write the regression test that reproduces the bug; it must fail for the reported reason.
2. Fix; the test goes green.
3. Run the surrounding suite so the fix did not move the bug elsewhere.

Guardrails

• DAMP over DRY: the failing output alone should say what broke.
• Deterministic only: no real time, no real network, no order dependence, no logic inside a test.
• Keep the pyramid: mostly unit, integration at real seams, few end-to-end.
• If a test is impossible (non-deterministic or environment-bound), say so plainly rather than implying coverage.
• Delegate mechanical scaffolding (boilerplate, fixtures, codemods) to a cheaper-tier subagent; keep the seam choice and the "is the behavior actually covered" judgment on the main model. A green suite is evidence, not proof.