This article explains how to set up a Dockerfile that will allow you to set up a Jenkins environment with slaves that allow for unit tests on multiple environments, with different PHP versions. Using Jenkins’ Swarm plugin allows for automatic detection of new slaves. So even developers can temporarily ‘lend’ their laptops for build jobs. The advantage of using Docker is that this will not interfere with their current installation because it is running inside an image.

Every PHP developer recognizes this problem: How do we make sure that all software remains working after a PHP upgrade. With the PHP 7 release on the horizon we were looking for solutions to run our unit tests on both PHP 5.x and 7.

http://devblog.simgroep.nl/blog/2015/11/12/jenkins-swarm-docker/