Agent-Skills.md

Agent Skills: Hybrid TDD

Write behavior-first tests in small vertical slices, with separate regression-test and fix commits for bugs.

UncategorizedID: edmundmiller/dotfiles/tdd

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edmundmiller/dotfiles
edmundmillerLicense: MIT
746

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pnpm dlx add-skill https://github.com/edmundmiller/dotfiles/tree/HEAD/skills/catalog/tdd

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skills/catalog/tdd/SKILL.md

Skill Metadata

Name
tdd
Description
"Write behavior-first tests in small vertical slices, with separate regression-test and fix commits for bugs."

Hybrid TDD

Core principles

  • Test behavior through public interfaces, not internals.
  • Work in vertical slices: one test → one implementation.
  • Keep CI green on every commit.
  • No speculative tests or speculative code.

Workflow

1) Plan with the user

Before coding, confirm:

  1. Interface changes needed
  2. Behaviors to test first (prioritized)
  3. Good seams/deep-module opportunities
  4. The first tracer bullet

2) Tracer bullet loop (feature work)

For each behavior:

  1. RED: write one failing behavior test
  2. GREEN: make the smallest change to pass
  3. MICRO-REFACTOR (optional): only while green
  4. Commit with a clear message showing progression

Rules:

  • One test at a time
  • Minimal code for current test only
  • Prefer integration-style behavior tests
  • Avoid coupling tests to implementation details

3) Bug-fix protocol (two commits)

  1. Add regression test that reproduces the bug and asserts intended behavior.
  2. Keep branch green by using strict xfail (XPASS must fail) or equivalent explicit expected-failure mechanism.
  3. Commit the regression test first (reviewers can verify the bug is captured).
  4. Implement the fix, remove expected-failure marker, verify test passes.
  5. Commit the fix separately.

4) Refactor phase

After target behaviors are green:

  • Extract duplication
  • Deepen shallow modules behind simpler interfaces
  • Run tests after each refactor step
  • Never refactor while red

Guardrails checklist

  • [ ] Test describes observable behavior
  • [ ] Test uses public interface
  • [ ] Test survives internal refactor
  • [ ] Code is minimal for this step
  • [ ] No red suite without explicit expected-failure marker
  • [ ] Deterministic tests; avoid hypothetical edge-case sprawl