python-testing-patterns Skill (wshobson) for Claude: What It Does and How to Install It

Makes Claude write Python tests the pytest way: fixtures, mocking, parametrized tests, async tests and CI setup.

Installs: 38.9K; on skills.sh
Stars: 42.1K; on GitHub
Files: 2; besides SKILL.md
Updated: Oct 2026; last repo commit

This skill is a testing guide for Claude, from wshobson's agents collection. It covers the arrange, act, assert structure, test isolation, fixtures, mocking with unittest.mock, parametrized tests, markers and coverage.

The main file keeps the basics. Worked examples are in references/details.md, and async, monkeypatch, property-based and database tests plus CI setup are in references/advanced-patterns.md. It loads when you write tests, set up a test suite or debug failing tests.

Good for

Python developers writing or fixing pytest suites
Teams setting up test infrastructure and coverage reports
Anyone practising test-driven development in Python
Developers mocking APIs, time or databases in tests

Install python-testing-patterns

Claude Code

Copy this prompt.

Install the python-testing-patterns skill in Claude Code. Run this command:

/plugin marketplace add wshobson/agents
/plugin install python-development@claude-code-workflows

Then check that it loaded and tell me how to use it.

2
Paste it into Claude Code. It shows the change and asks before running it.

Pick one route. The plugin routes install the whole python-development plugin: 3 agents, 1 command and 16 skills (counted from the plugin folder in the repo tree, which has no hooks or MCP config files). The skills-only routes install just this skill, with no agents or commands. The skill needs Python and pytest in your own project.

From the project README. Source.

What's in the skill

When it loads

Implement comprehensive testing strategies with pytest, fixtures, mocking, and test-driven development. Use when writing Python tests, setting up test suites, or implementing testing best practices.

Sections in SKILL.md

When to Use This Skill
Core Concepts
1. Test Types
2. Test Structure (AAA Pattern)
3. Test Coverage
4. Test Isolation
Quick Start
Detailed patterns and worked examples
Testing Best Practices
Test Organization
Test Naming Convention
Testing Retry Behavior
Mocking Time with Freezegun
Test Markers
Coverage Reporting

Key facts

Author: wshobson (repo owner)
License: MIT
Installs on skills.sh: 38,856 (Nov 2, 2026)
GitHub stars: 42,081 for the whole wshobson/agents repo (Nov 2, 2026)
Last repo commit: Oct 30, 2026
What it includes: 3 files including SKILL.md: references/details.md and references/advanced-patterns.md (no scripts)
Needs: Python and pytest in your project. The examples also use freezegun
Part of: The python-development plugin (version 1.2.4) in wshobson/agents. Counted from the plugin folder: 3 agents, 1 command and 16 skills
Works in: Claude Code, Codex CLI, Cursor, OpenCode, Antigravity CLI, GitHub Copilot and Pi, per the README. Skills-only installers ask which tool you use

What it includes

Unit, integration, functional and performance tests
Explains Arrange, Act, Assert, coverage and why tests must be independent.
Try: “Write pytest tests for this payment module with fixtures for the database.”
Read · Test types and AAA
Setup and teardown with fixtures (details.md)
Worked examples of simple tests and fixtures that clean up after themselves.
Write · Basic pytest and fixtures
One test, many inputs
Uses parametrize and pytest.param for special cases.
Write · Parameterized tests
unittest.mock for APIs and services
Includes testing retry behavior with mock side effects.
Write · Mocking
Checks that errors are raised
Part of the fundamental patterns in details.md.
Write · Testing exceptions
freezegun and pytest markers
Freezegun controls time in tests. Markers group and filter tests.
Write · Time and markers
Async, monkeypatch, temp files, conftest, property-based, database
Reference guide in references/advanced-patterns.md.
Read · Advanced patterns
GitHub Actions workflow, pytest.ini and pyproject.toml
Also in advanced-patterns.md, along with coverage reporting.
Read · CI and configuration

From the official docs

Permissions

Low risk

What it can do

Read your data
Create and change things
Delete things
Read-only mode

Watch out for

The examples install Python packages
SKILL.md has a coverage example that starts with pip install pytest-cov, and advanced-patterns.md has a CI workflow with pip install -e ".[dev]" and pip install pytest pytest-cov. Install into a virtual environment and review any command before it runs. github.com
A CI workflow example would add a file under .github
advanced-patterns.md shows a .github/workflows/test.yml. If you ask for CI setup, review that file before you commit it. github.com
The plugin route installs more than this skill
The python-development plugin has 3 agents, 1 command and 16 skills. We found no hooks or MCP config files in its folder. The skills-only routes install only this skill. github.com

Security advisories

No published security advisories as of Nov 2, 2026.

Technical details

Turning on read-only	No read-only mode. Use version control.
Talks to	Package downloads when you run the pip install commands. Whatever your own tests call
Sign-in and keys	SKILL.md and the two reference files do not mention any account or key. The examples read an optional DATABASE_URL environment variable inside test code.
Scopes	Claude can write test files and edit your project when you ask for tests The examples run pytest and the coverage commands ask you to pip install pytest-cov The CI example in advanced-patterns.md is a GitHub Actions workflow that runs pip install

Questions

What does the python-testing-patterns skill do?

It gives Claude a pytest playbook. Claude uses it to write unit and integration tests, fixtures, mocks and parametrized cases, and to set up coverage and CI.

How do I install python-testing-patterns?

Use the install box at the top of this page. It lists the plugin route and two skills-only commands: npx skills add wshobson/agents --skill python-testing-patterns and gh skill install wshobson/agents python-testing-patterns (GitHub CLI 2.90 or later), which skip the plugin's agents and commands.

Is this skill from Anthropic?

No. It is in wshobson/agents, a community collection. The skill sits in the python-development plugin there.

Should I install the whole python-development plugin?

Only if you want the rest. The README documents a plugin route for Claude Code and Codex. The plugin folder holds 3 agents, 1 command and 16 skills, and the repo tree shows no hooks or MCP config files in it. The install box offers the plugin and skills-only commands.

Does it only cover pytest?

Mostly. The description names pytest, fixtures, mocking and test-driven development, and the examples use pytest, unittest.mock and freezegun.

Does it work in Codex or Cursor?

The README documents Codex CLI as a plugin route and a skills-only install. For Cursor it points to a plugin marketplace and its setup docs, which we did not check, so follow the README there.

Is it safe?

Installing it runs nothing: it is a guide with two reference files and no scripts. When you ask for tests, Claude writes and may run them in your project. The examples use pip install pytest-cov and a CI workflow with pip install, so review those commands and any files it adds.

Information

updated Nov 2, 2026

Repository: wshobson/agents
Folder: plugins/python-development/skills/python-testing-patterns

wshobson/agents skills.sh

Sources

Docs, issue trackers and discussions this page is built from.

Show all 5

python-testing-patterns SKILL.md · github.com
wshobson/agents README · github.com
python-development plugin.json · github.com
details.md · github.com
advanced-patterns.md · github.com