Joomla maintains a range of different methods to run automated tests on its codebase.
The unit tests are checking the specific PHP code of the Joomla framework with the help of PHPUnit. For further information on the tests and on how to run them, please check out tests/unit/README.md
The javascript tests test the Joomla-specific Javascript code. For further information on the tests and on how to run them, please check out https://docs.joomla.org/Special:MyLanguage/Running_JavaScript_Tests_for_the_Joomla_CMS
The Codeception tests test the user interface in a real browser and the webservices API of Joomla with the help of Codeception. For further information on the tests and on how to run them, please check out tests/Codeception/README.md