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]
envlist = ["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