Agent-Skills.md

Agent Skills: TDD Python Skill

Python Test-Driven Development expertise with pytest, strict red-green-refactor methodology, domain-first modeling (DDD), principled DRY discipline, FastAPI testing patterns, and Pydantic model testing. Use when implementing Python features with TDD, writing pytest tests, testing FastAPI endpoints, developing with test-first approach, modeling domain concepts, refactoring duplication, or when user mentions 'Python TDD', 'pytest', 'FastAPI testing', 'red-green-refactor', 'Python unit tests', 'test-driven Python', 'domain modeling', 'value object', 'ubiquitous language', 'DRY', or 'Python test coverage'.

UncategorizedID: greyhaven-ai/claude-code-config/tdd-python

Repository

greyhaven-ai/claude-code-config
greyhaven-aiLicense: MIT
294

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pnpm dlx add-skill https://github.com/greyhaven-ai/claude-code-config/tree/HEAD/grey-haven-plugins/core/skills/tdd-python

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grey-haven-plugins/core/skills/tdd-python/SKILL.md

Skill Metadata

Name
tdd-python
Description
"Python Test-Driven Development expertise with pytest, strict red-green-refactor methodology, domain-first modeling (DDD), principled DRY discipline, FastAPI testing patterns, and Pydantic model testing. Use when implementing Python features with TDD, writing pytest tests, testing FastAPI endpoints, developing with test-first approach, modeling domain concepts, refactoring duplication, or when user mentions 'Python TDD', 'pytest', 'FastAPI testing', 'red-green-refactor', 'Python unit tests', 'test-driven Python', 'domain modeling', 'value object', 'ubiquitous language', 'DRY', or 'Python test coverage'."

TDD Python Skill

Python Test-Driven Development following strict red-green-refactor cycle with pytest — sharpened by DDD at Red (model the domain first) and DRY at Refactor (deduplicate same-concept repetition only).

Description

Systematic Python implementation using TDD methodology. Tests are written first and drive design; domain vocabulary drives the tests; duplication is removed only when the same concept repeats, not when syntax coincidentally looks alike.

Discipline Layering

  • Before Red — Model the Domain: Name the entity, value object, or aggregate in the business's language. Decide entity vs. value object. Reject primitive obsession — wrap str/int in EmailAddress, Money, NewType, or pydantic.BaseModel when they carry rules. Keep domain logic out of FastAPI routes.
  • Red: Write a failing test. Name it in domain terms (test_rejects_refund_when_amount_exceeds_daily_limit) — never mechanical (test_returns_false).
  • Green: Minimal code to pass. No speculative abstractions.
  • Refactor — DRY with discipline: Deduplicate only when the same domain concept appears ≥3 times with the same meaning. Three similar lines beats a premature abstraction. Promote recurring primitives to value objects. When uncertain, inline.

What's Included

  • Examples: Python TDD cycles, FastAPI TDD, Pydantic model TDD, value-object modeling
  • Reference: pytest patterns, Python testing best practices, branded-type idioms (NewType, frozen=True)
  • Templates: pytest templates, TDD workflows

Use When

  • Implementing Python features with TDD
  • Modeling domain concepts (entities, value objects, aggregates)
  • FastAPI endpoint development (keeping domain rules out of routes)
  • Pydantic model development
  • Refactoring duplication after a green test

Related Agents

  • tdd-python-implementer

Skill Version: 1.1