Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

You can contribute in many ways:

Types of Contributions

Report Bugs

Report bugs at

If you are reporting a bug, please include:

  • Your operating system name and version.
  • Any details about your local setup that might be helpful in troubleshooting.
  • Detailed steps to reproduce the bug.

The issue template will tell you how to collect version information.

Fix Bugs

Look through the GitHub issues for bugs. Anything tagged with “bug” and “help wanted” is open to whoever wants to implement it.

Implement Features

Look through the GitHub issues for features. Anything tagged with “enhancement” and “help wanted” is open to whoever wants to implement it.

Write Documentation

marbles could always use more documentation, whether as part of the official marbles docs, in docstrings, or even on the web in blog posts, articles, and such.

Submit Feedback

The best way to send feedback is to file an issue at

If you are proposing a feature:

  • Explain in detail how it would work.
  • Keep the scope as narrow as possible, to make it easier to implement.

Build a Plugin

We’ve developed marbles in a pluggable way, so you can contribute to the marbles ecosystem without committing code to the marbles repo!

Just as marbles provides some mixins you can add to a unittest.TestCase by adding a superclass to your test, you can develop more mixins outside the marbles repo and publish them yourself, they’ll interoperate just fine. Of course, we’d like to include mixins which may be useful to many people in the marbles.mixins package, so if you think that’s the case, please send us a pull request.

The marbles annotation logging mechanism right now just writes JSON structured data to a file. You can use logstash, mongoimport, Spark, or any other tool that understands JSON to store and analyze them after the fact. But, you can also implement the marbles logging interface to do something else with the assertion metadata, instead of logging it to disk. If you’d like to share your logging plugin, or discuss ideas for how to build one, just open an issue and we can discuss it with you there.

Get Started!

Ready to contribute? Here’s how to set up marbles for local development.

  1. Fork the marbles repo on GitHub here.

  2. Clone your fork locally:

    $ git clone
  3. Install your local copy into a virtualenv. If you have pipenv installed, you can run:

    $ cd marbles/
    $ pipenv install --dev
    $ pipenv shell

    This will install all of the marbles development dependencies, install marbles in development mode, so your changes to the files in your clone will take effect immediately, and put you in a shell where you can run the tests, build the docs, etc.

    If you don’t use pipenv, you can get the same effect inside any other virtualenv by running:

    $ pip install -r requirements.txt
  4. Create a branch for local development:

    $ git checkout -b name-of-your-bugfix-or-feature-or-docs

    Now you can make your changes locally. marbles is developed as separate packages in the namespace package marbles:

    1. The TestCase customizations and the assertion logging infrastructure live in marbles.core, which you’ll find inside the repo under marbles/core.
    2. The mixins live in marbles.mixins, which you’ll find inside the repo under marbles/mixins.
  5. As you make changes, you can run the tests and lint with flake8. These should be run inside the package you’ve made changes to, so if you’ve made changes to marbles.core, you should run this:

    $ cd marbles/core
    $ python flake8
    $ python test


    Don’t worry about bumping version numbers yourself. We’ll handle this in the release that includes your changes.

    For more developer workflows (linting, testing, test coverage, docs), see Maintainer’s Guide.

  6. Commit your changes and push your branch to GitHub:

    $ git add .
    $ git commit -m "Your detailed description of your changes."
    $ git push origin name-of-your-bugfix-or-feature
  7. Submit a pull request through the GitHub website.

  8. We’ll review your changes, merge them, and include them in the next release.

Pull Request Guidelines

Before you submit a pull request, check that it meets these guidelines:

  1. The pull request should include tests.
  2. If the pull request adds functionality, the docs should be updated. Make sure your new functionality is documented with docstrings and appropriate additions to the Sphinx docs, and add the feature to the list in
  3. The pull request should work for Python 3.5, 3.6, and 3.7. Check and make sure that the tests pass for all supported Python versions.
  4. In order to accept your code contributions, please fill out the appropriate Contributor License Agreement in the cla folder and submit it to We need this before we can accept your pull request.