purpose-first-tdd

name	purpose-first-tdd
description	Use when making or evaluating any behavior, plan, prompt, skill, code, test, or operational change that needs purpose, proof, consumer, or falsifier clarity.

Purpose First TDD

If dispatched as a subagent for a specific task, skip this skill.

Purpose comes first. Tests are executable purpose. Code and instructions exist to satisfy a real consumer.

Redteam forwarder: For falsifier validation, run /redteam:verify to cross-check that the falsifier actually catches the intended failure mode. A falsifier that never fires is not a real falsifier. For high-stakes contracts (security, billing, policy gates), use /redteam:review to validate the contract holds before declaring it done.

Purpose: make every change defensible before implementation. Consumer: agents planning, implementing, reviewing, debugging, or editing instructions. Failure consequence: changes optimize activity instead of value; tests prove implementation details instead of purpose; reviewers cannot tell what failure means. Falsifier: the change is purely cosmetic or self-contained with no behavior, policy, proof, consumer, or public-contract impact.

Contract

Before behavior changes, fill the canonical 9-field PDD contract:

• purpose: why this exists.
• consumer: who or what uses it.
• contract: what the change must achieve.
• failureBoundary: what breaks or is contained when it fails.
• evidence: test, command, observation, trace, or invariant proving it.
• falsifier: executable or observable condition that would prove it wrong.
• nonGoals: what this intentionally excludes.
• invariants: truths that must remain true while changing it.
• assumptions: facts not yet proven.

TDD Rule

For behavior, plan, prompt, skill, code, test, or operational changes:

1. Write or identify failing proof from the evidence/falsifier fields.
2. Run it and see the expected failure.
3. Implement the smallest change.
4. Run proof again and relevant regression checks.

If the task is operational/config-only, define the equivalent proof command or live-state check before changing it.

Judgment Rule

Any judgment call needs confidence and falsifier:

confidence=<level>; falsifier=<specific evidence that would change this>.

No falsifier means the decision is not ready.