How to use the command 'tox' (with examples)

Tox is a command-line tool that allows you to automate Python testing across multiple Python versions. It uses a tox.ini file to configure different testing environments and provides a test command for running tests in these environments.

Use case 1: Run tests on all test environments

Code:

tox

Motivation: Running tests on all test environments ensures that your code is compatible across different Python versions. This is especially useful when developing cross-platform Python applications or libraries.

Explanation: The command tox without any arguments runs the tests on all the defined test environments specified in the tox.ini file.

Example output:

GLOB sdist-make: /path/to/project/setup.py
...
py36 passed
py37 passed
...

Use case 2: Create a tox.ini configuration

Code:

tox-quickstart

Motivation: Creating a tox.ini configuration file is necessary to define the desired test environments and test commands. The tox-quickstart command provides a quick and interactive way to generate a basic tox.ini file.

Explanation: The command tox-quickstart guides you through a series of prompts to create a tox.ini configuration file. It asks for basic information such as the project name, test environments, and dependencies.

Example output:

Creating initial config file in /path/to/project/tox.ini

Use case 3: List the available environments

Code:

tox --listenvs-all

Motivation: Listing the available environments is useful when you want to verify the defined test environments in your tox.ini file.

Explanation: The --listenvs-all option provides a detailed list of all the available test environments defined in the tox.ini file, including the inherited environments.

Example output:

py36
py37
...

Use case 4: Run tests on a specific environment

Code:

tox -e py36

Motivation: Running tests on a specific environment allows you to test your code against a particular Python version or a specific test environment defined in your tox.ini file.

Explanation: The -e option allows you to specify the test environment to run. In this example, the tests will be executed on the ‘py36’ environment, which corresponds to Python 3.6.

Example output:

Running tests in environment: py36
...

Use case 5: Force the virtual environment to be recreated

Code:

tox --recreate -e py27

Motivation: Recreating the virtual environment is beneficial when you need to ensure that the environment is clean and up-to-date. It can be useful to troubleshoot issues related to dependencies or when you want to start fresh.

Explanation: The --recreate option forces the virtual environment to be recreated before running the tests. In this example, the tests will be executed on the ‘py27’ environment, which corresponds to Python 2.7.

Example output:

Recreating virtualenv...
...

Conclusion:

Tox is a powerful tool for automating Python testing across multiple Python versions. By using the tox command with various options, you can run tests on different environments, create configuration files, list available environments, and force virtual environment recreation when needed. This helps ensure your code is compatible with different Python versions and maintain a consistent testing workflow.