test-driven-development

name	test-driven-development
description	Repo-local TDD workflow for Zoolanding Lambda implementation work. Use before behavior-changing handler or helper code changes. Skip as the default path for docs-only or SAM-config-only edits.
user-invocable	true

Test-Driven Development

Write the failing proof first, then write the smallest code that makes it pass.

Default Scope In This Repo

Use this for:

• handler behavior changes
• helper logic changes
• request validation or response behavior changes
• storage-contract changes that can be pinned to a reproducible event

Do not treat this as the default path for:

• docs-only changes
• SAM-config-only changes with no behavior change

Workflow

1. Define the failing proof first.

   • Add or update the narrowest payload check or local harness case that demonstrates the intended behavior change.
   • If the repo lacks unit tests for the area, create the smallest reproducible event before implementation.

2. Verify the proof fails for the right reason.

   • Confirm the failure matches the missing or broken behavior.
   • Fix the test if it fails because of setup noise instead of the intended reason.

3. Write the minimal implementation.

   • Change only the code needed to satisfy the failing proof.
   • Avoid speculative helpers and unrelated cleanup.

4. Re-run the narrow proof.

   • Confirm the targeted test or harness case now passes.

5. Run the smallest adjacent regression check.

   • Add one nearby test or focused verification step when the change could break adjacent behavior.

6. Refactor only after green.

   • Keep behavior unchanged while improving structure.

Repo-Specific Guidance

• Pair this skill with karpathy-guidelines for scope control.
• Use focused payload fixtures when a full test harness is not present.