Docker Container for System Tests
From Joomla! Documentation
The Automated Tests Working Group is working on a Docker Container containing Selenium and all the tools needed to run the tests.
What is Docker and what has to do with Joomla?
The concept of Docker is difficult to explain but if you know what Virtual Machines are, the concept is similar. Basically we have a virtual environment to execute applications inside a real environment. In Joomla we use Docker to create different instances of a preconfigured environment so we can run the many hours of tests that we have in parallel. One suite in each container. To learn more about docker check: https://www.docker.com/whatisdocker/
The Joomla System Testing Docker Container
Before being able to run the System Tests on your machine you need to Install Docker.
After having Docker set up in your system you can get the Joomla System Tests Docker container. You can find it at: https://github.com/joomla-projects/joomla-systemtest-env/blob/master/README.md
This is a Docker Image with Selenium Server, Xvfb, Firefox and Chromium installed. SeleniumEnv was created to run Selenium tests without installing Selenium and its dependencies. Selenium server is executed inside a container and connected from a host machine.