Buildbot is a software development continuous integration tool which automates the compile/test cycle required to validate changes to the project code base.
Jenkins is a self-contained Java-based program, ready to run out-of-the-box, with packages for Windows, Mac OS X and other Unix-like operating systems.
Buildkite is a CI and build automation tool that combines the power of your own build infrastructure with the convenience of a managed, centralized web UI.
