tox

Installation and Setup

Install it from the Python Package Index (PyPI):

• Windows
• Linux + macOS

PS> py -m pip install tox

$ python -m pip install tox

Key Features

• Creates isolated environments and runs test, lint, format, and other automation commands inside them.
• Selects multiple Python versions in a single run via environment names and the configured environment list.
• Builds and installs your project into environments to validate packaging and installation.
• Runs environments in parallel when requested to speed up local workflows and CI.
• Fits CI pipelines with reproducible environments, explicit configuration, and meaningful exit codes.

Usage

The tox tool discovers configuration in tox.ini, tox.toml, or pyproject.toml. A minimal pyproject.toml that runs tests on two Python versions and a linter looks like this:

[tool.tox]
env_list = ["py313", "py314", "lint"]

[tool.tox.env.py313]
deps = ["pytest"]
commands = [["pytest", "-q"]]

[tool.tox.env.py314]
deps = ["pytest"]
commands = [["pytest", "-q"]]

[tool.tox.env.lint]
deps = ["ruff"]
commands = [["ruff", "check", "."]]

Run all configured environments:

$ python -m tox

Run a specific environment:

$ python -m tox -e py313

Run environments in parallel using available CPUs:

$ python -m tox -p auto

Recreate environments when dependencies or settings change:

$ python -m tox -r

Related Resources

Course

Testing Your Code With pytest

In this video course, you'll learn how to take your testing to the next level with pytest. You'll cover intermediate and advanced pytest features such as fixtures, marks, parameters, and plugins. With pytest, you can make your test suites fast, effective, and less painful to maintain.

intermediate testing tools