tdd

name	tdd
description	Apply when the task requires implementing net-new behavior — features, modules, endpoints, integrations, or any additive change. Drives development through strict red-green-refactor with test-first slicing and deterministic verification.

TDD Skill

Strict red-green-refactor for all net-new behavior. Test-first, one behavior slice at a time.

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Constraints

• Test-first — no production code without a failing test that demands it.
• Minimal diff — no unrelated refactors, renames, or formatting churn.
• Deterministic — control time, randomness, I/O, and concurrency via seams/fakes.
• Fail fast — no silent error swallowing without a test proving the intent.

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Cycle

Per behavior slice, execute the canonical red-green-refactor loop:

1. Red — one test, failing for the right reason. Name encodes behavior + condition.
2. Green — minimum production code to pass. No speculative abstraction (Rule of Three).
3. Refactor — remove duplication, tighten names, simplify flow. Behavior unchanged.
4. Verify — run smallest relevant target first, then full suite. Report commands + outcomes.

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Output

• Intent: one sentence.
• Test slices: 3-7 bullets, ordered.
• Changes: tests added/updated + production code, by file.
• Verification: commands + pass/fail.
• Risks: contract changes, flaky-test vectors, uncovered boundaries.