Security provides an infrastructure for sophisticated authorization systems, which makes it possible to easily separate the actual authorization logic from so called user providers that hold the users credentials. It is inspired by the Java Spring framework.
Documentation:
https://symfony.com/doc/3.0/book/security.html
You can run the unit tests with the following command:
$ cd path/to/Symfony/Component/Security/Acl/
$ composer.phar install --dev
$ phpunit