tox

Language: Python

CLI/Utils

tox was created to standardize testing in Python projects and simplify the management of virtual environments for testing purposes. It is widely used in open-source projects to ensure that code runs correctly on multiple Python versions and environments.

tox is a Python tool for automated testing in multiple environments. It allows developers to run tests across different Python versions and dependency configurations, ensuring compatibility and reliability.

Installation

pip: pip install tox
conda: conda install -c conda-forge tox

Usage

tox automates creating virtual environments, installing dependencies, running tests, and reporting results. It reads configuration from a `tox.ini` file where you define environments, dependencies, and test commands.

Creating a basic tox.ini

[tox]
envlist = py38, py39

[testenv]
deps = pytest
commands = pytest

Defines two environments (Python 3.8 and 3.9) that install pytest and run the test suite.

Running tox

# In terminal:
tox

Creates virtual environments for each Python version defined in `envlist` and runs the specified test commands.

Specifying different dependencies per environment

[testenv:py38]
deps = pytest==6.2.5

[testenv:py39]
deps = pytest==7.0.0

Demonstrates how to install specific versions of dependencies for different Python versions.

Passing environment variables

[testenv]
setenv = DJANGO_SETTINGS_MODULE=myproject.settings
commands = pytest

Sets environment variables within the virtual environment before running tests.

Running multiple commands

[testenv]
deps = flake8
commands = flake8 src tests
           pytest

Runs linting with flake8 followed by pytest in the same environment.

Error Handling

InterpreterNotFound: Ensure the specified Python versions are installed and accessible in your PATH.
Dependency installation failed: Verify that dependencies are correctly specified and available on PyPI or other indexes.
Command failed: Check the command syntax and ensure all necessary dependencies are installed in the environment.

Best Practices

Use tox to test your code against all supported Python versions.

Keep your `tox.ini` file simple and modular to avoid complexity.

Combine linting, testing, and coverage in tox environments.

Use `skip_missing_interpreters = true` to avoid failures if a Python version isn’t installed.

Integrate tox with CI/CD pipelines for automated testing.

Official DocsGithub