# Python Testing

> Consult this skill for Python testing implementation and patterns. Use when writing unit tests, setting up test suites, implementing TDD, configuring pytest, creating fixtures, async testing, writing integration tests, mocking dependencies, parameterizing tests, setting up CI/CD testing. Do not use when evaluating test quality - use pensive:test-review instead. DO NOT use when: infrastructure test config - use leyline:pytest-config.

- Skill: `micsapp/python-testing` (Agent Skill, multi-file: 7 files)
- Install (CLI): `npx skillmds@latest add micsapp/python-testing`
- Raw SKILL.md: https://api.skillmd.com/api/skills/micsapp/python-testing/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: micsapp (https://skillmd.com/u/micsapp)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/micsapp/python-testing

---

# Python Testing Hub

Testing standards for pytest configuration, fixture management, and TDD implementation.

## Table of Contents

1. [Quick Start](#quick-start)
2. [When to Use](#when-to-use)
3. [Modules](#modules)

## Quick Start

1.  **Dependencies**: `pip install pytest pytest-cov pytest-asyncio pytest-mock`
2.  **Configuration**: Add the following to `pyproject.toml`:
    ```toml
    [tool.pytest.ini_options]
    testpaths = ["tests"]
    addopts = "--cov=src"
    ```
3.  **Verification**: Run `pytest` to confirm discovery of files matching `test_*.py`.

## When To Use

- Constructing unit and integration tests for Python 3.9+ projects.
- Isolating external dependencies using `pytest-mock` or custom monkeypatching.
- Validating asynchronous logic with `pytest-asyncio` markers and event loop management.
- Configuring project-wide coverage thresholds and reporting.

## When NOT To Use

- Evaluating test
  quality - use pensive:test-review instead
- Infrastructure test
  config - use leyline:pytest-config
- Evaluating test
  quality - use pensive:test-review instead
- Infrastructure test
  config - use leyline:pytest-config

## Modules

This skill uses modular loading to manage the system prompt budget.

### Core Implementation
- See `modules/unit-testing.md` - AAA (Arrange-Act-Assert) pattern, basic test structure, and exception validation.
- See `modules/fixtures-and-mocking.md` - Request-scoped fixtures, parameterization, and boundary mocking.
- See `modules/async-testing.md` - Coroutine testing, async fixtures, and concurrency validation.

### Infrastructure & Workflow
- See `modules/test-infrastructure.md` - Directory standards, `conftest.py` management, and coverage tools.
- See `modules/testing-workflows.md` - Local execution patterns and GitHub Actions integration.

### Standards
- See `modules/test-quality.md` - Identification of common anti-patterns like broad exception catching or shared state between tests.

## Exit Criteria

- Tests implement the AAA pattern.
- Coverage reaches the 80% project minimum.
- Individual tests are independent and do not rely on execution order.
- Fixtures are scoped appropriately (function, class, or session) to prevent side effects.
- Mocking is restricted to external system boundaries.

## Troubleshooting

- **Test Discovery**: Verify filenames match the `test_*.py` pattern. Use `pytest --collect-only` to debug discovery paths.
- **Import Errors**: Ensure the local source directory is in the path, typically by installing in editable mode with `pip install -e .`.
- **Async Failures**: Confirm that `pytest-asyncio` is installed and that async tests use the `@pytest.mark.asyncio` decorator or corresponding auto-mode configuration.