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greyhaven-ai (@greyhaven-ai-claude-code-config) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Tdd Python by greyhaven-ai-claude-code-config

Name: Tdd Python
Rating: 4.5 (4 reviews)
Author: greyhaven-ai

Tdd Python

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'.

greyhaven-ai Updated Sep 10, 2026

File contents

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

---name: tdd-pythondescription: 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 SkillPython 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).## DescriptionSystematic 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

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