# Testing Pytest > Python pytest adapter for TDD workflows. Use this skill when users need pytest test design, red-green-refactor execution, fixture/parametrize strategy, or CI test quality improvements in Python projects. Use when this capability is needed. - Skill: `tomevault-io/testing-pytest` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/testing-pytest` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/testing-pytest/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/testing-pytest --- ## Use when - Project uses Python + pytest. - User asks to write/refactor/debug tests with pytest. - User asks for TDD in Python. - User asks for fixture design, flaky test fixes, coverage, or performance checks in pytest. ## Avoid when - Scope is not Python/pytest. - User asks for language-agnostic TDD only (use `tdd-core` first). ## Relationship to tdd-core - Apply `tdd-core` as the base doctrine. - This skill adds pytest-specific execution patterns. ## Pytest-specific workflow 1. Pick one behavior from the TDD plan. 2. **RED**: add one failing pytest test. 3. **GREEN**: minimal implementation to pass. 4. **REFACTOR**: clean code/fixtures while tests stay green. 5. Repeat in small vertical slices. ## Pytest guardrails - Prefer public-interface tests over internals. - Use `@pytest.mark.parametrize` for behavior matrices. - Use Hypothesis for invariants/properties. - Keep fixtures explicit by scope; avoid hidden coupling in `conftest.py`. - Use boundary mocks only; avoid mocking your own domain modules. See [TDD_REFERENCE.md](TDD_REFERENCE.md) for commands and troubleshooting. ## Output - Behavior coverage for this cycle - Test files/fixtures changed - Commands run + results - Remaining gaps/risks + next cycle --- > Source: [pesap/agents](https://github.com/pesap/agents) — distributed by [TomeVault](https://tomevault.io).