Continuous integration is a great way to ensure that the application stays bug-free at every development iteration. The main idea behind continuous integration is to run the test suite for the project very frequently, usually on a separate build server that pulls the code directly from the main project repository.
Setting up a build server can be accomplished by manually setting up software such as Jenkins (https://jenkins.io/), Buildbot (http://buildbot.net/), and Drone (https://github.com/drone/drone) on a machine. This a convenient and cheap solution, especially for small teams and private projects.
Most open source projects take advantage of Travis CI (https://travis-ci.org/), a service capable of building and testing your code automatically from your repository because it's tightly integrated with GitHub. As of today, Travis CI provides a free plan for open source projects. Many...