Skip to content

Testing

Python’s testing story centers on pytest, but the supporting cast — parallel runners, version matrices, and CI — is just as important. The handbook covers setup, day-to-day usage, and the orchestrators that wrap pytest in modern uv-based workflows.

Get started with pytest

Set up pytest with uv
Initial pytest configuration
Run tests with uv
The everyday command
pytest reference
Quick facts about pytest

Parallel and matrix testing

Parallel tests
Speed up suites with xdist
Test multiple Python versions
Matrix testing without tox
Tox/nox in a uv world
When orchestrators still earn their keep

More Testing pages

Everything else tagged testing, grouped by section. Pages featured above are not repeated here.

Tutorial

Build and Publish a Python Package with uv, Ruff, Pyrefly, pytest, and GitHub Actions

Build a Python library with uv, Ruff, Pyrefly, and pytest. Set up CI/CD with GitHub Actions. Publish to PyPI with trusted publishing.

Set up a complete Python project with uv, Ruff, Pyrefly, pytest, and pre-commit

Tutorial: build a Python project from scratch with uv, Ruff, Pyrefly, pytest, and pre-commit. Set up linting, type checking, and testing.

Set up a Python project optimized for Claude Code

Build a Python CLI agent that understands your codebase and fixes bugs autonomously using Claude Code.

How To

How to Combine Coverage Across a CI Matrix

Aggregate coverage.py from GitHub Actions matrix jobs into one report, post to run summary, gate with single threshold.

How to configure Claude Code to run your pytest suite

Wire pytest into Claude Code with Stop hooks for fast feedback. Sparse tracebacks help agents fix failures efficiently.

How to configure Cursor for pytest

Enable pytest in Cursor's Testing sidebar, configure test discovery with pyproject.toml, and add a Cursor rule so the AI agent always runs tests via uv.

How to Fix Common pytest Errors with uv

Diagnose and fix ModuleNotFoundError, conftest issues, collection warnings, and other common pytest problems in uv-managed projects.

How to Measure Code Coverage with pytest-cov

Measure test coverage with pytest-cov and enforce minimum thresholds. Configure coverage reporting in pyproject.toml and integrate with CI pipelines.

How to Parameterize Tests with pytest

pytest.mark.parametrize: run same test logic across multiple inputs with custom IDs, stacked decorators, and indirect fixtures.

How to replace tox with uv and a Makefile

Replace tox with uv and Make for faster multi-Python testing. Parallel test runs with minimal configuration overhead.

How to use uv to speed up tox

Install the tox-uv plugin to replace pip and virtualenv with uv, making tox environment creation and dependency installation 10-100x faster.

Explanation

Essential pytest Plugins

pytest plugins for reliable test suites: detect test-order bugs, kill hangs, retry flakes, and track performance regressions.

pytest vs unittest: Which Should You Use?

pytest cuts unittest's boilerplate with plain assert and reusable fixtures, so tests are faster to write and easier to read.

Reference

nox

Nox: Python test automation tool using Python code for configuration. Supports uv backend, pyproject.toml, multi-version matrices.

tox-uv

tox-uv is a tox plugin that replaces pip and virtualenv with uv for faster environment creation and dependency installation.

tox

tox automates tests across Python versions. Isolate and test your library on 3.10–3.14 in one command for CI reliability.

From the blog

Posts tagged testing.

Last updated on