Continuous Integration

Continuous Integration is a practice in which the team checks in and builds the software system as often as possible. This keeps all the programmers on the same page, and enables very rapid progress. Perhaps surprisingly, integrating more frequently tends to eliminate integration problems that plague teams who integrate less often.

The concept of frequent integration has been around for many years - Steve McConnell of Microsoft wrote about daily builds in 1993's Code Complete. However, XP teams integrate as often as is possible, ideally as soon as a change is checked in to the code repository.

There are several tools that assist in Continunous Integration:

among others. Each of these tools can be configured to poll your code repository for changes, and automatically start the build process when a change is detected. They can also execute unit and accpetance tests, and report the results.

There is also the belief that a tool is overkill for implementing Continuous Integration. James Shore has published a Continuous Integration Checklist, that thoroughly describes the CI process without the use of special tool (excepting a rubber chicken!).

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