Continuous integration is a practice where every developer integrates their own work with that of the other developers in the team at least once a day and preferably more often. This means that every developer should push their work to the repository at least once a day and a continuous integration build verifies that their work compiles and that all unit tests run. It is important to understand that this verification should not run only on the code that the developer is working on in isolation. The real value comes when the work is also integrated with the work of others.

When integrating changes often and fast, problems with merging changes are less frequent and if they occur, are often less difficult to solve. In Chapter 2, Everything Starts with Source Control, you will learn more about how to set up your source control repositories to make this possible. In Chapter 3, Moving to Continuous Integration, you will learn about setting up a continuous integration build.