At Codeception we are glad to receive contributions and patches from the community. There are a few guidelines that we need contributors to follow so that we can have a chance of keeping on top of things.
Please check the guide for sending your contributions with Github at https://github.com/Codeception/Codeception/wiki/Git-workflow-for-Codeception-contributors
All contributions must follow the coding standards described at: https://github.com/Codeception/Codeception/wiki/Codeception-coding-style-standard
Bugfixes should be sent to to current stable branch, which is the same as major version number.
Breaking features and major improvements should be sent into master. When you send PRs to master, they will be added to release cycle only when the next stable branch is started.
Check also the "tests/README.md" to learn more about the available internal Codeception tests.
If you want to contribute documentation to the guides you are asked to send your changes to the /docs/ folder: https://github.com/Codeception/Codeception/tree/2.0/docs. This files are the source for the codeception website guides: http://codeception.com/docs/01-Introduction. Remind to send your documentation improvements to the right "repository branch" depending on the Codeception version you are working with: 2.0, master,...
The documentation for each module is directly generated from the corresponding docblock which can be found in each module (src/Module/Codeception/*.php).