In any decent sized project, the more times you commit code, the bigger the chance is that you will break something. Call it the law of unintended consequences or the butterfly effect, but the fact is that in complex systems, we cannot anticipate all the effects of a change. To deal with this we can either adopt the "release and pay" method of software control, or we can setup systems to help us find the consequences of our actions, so we that can correct them before they become a problem. We usually call these systems Continuous Integration systems.
