Importance of Continuous Integration

I encountered an incredibly interesting situation recently that clearly illustrates the importance of Continuous Integration. Two separate teams were each working on separate software modules. Eventually, these teams knew they’d need to integrate the two modules into a larger whole. Unfortunately, communication wasn’t that great between the two teams, and while they each had a robust suite of unit tests (they created stubs when testing the integration points between each other), and regularly tested their individual components, they did not ever test them together. Finally, the day came (late in the project, mind you), when the two teams needed to integrate. In fact, integration even went fairly well, with the two modules able to communicate between each other without many problems. Integration testing revealed something alarming, however. A major piece of functionality was missing. Each team thought the other was providing that behavior.

The moral of the story, of course, is that had these separate teams been focused on integrating their two components early and often, this problem would have been discovered much earlier in the development lifecycle. But working in silos is easy and integration is hard. By creating a false sense of progress by avoiding integration until late in the lifecycle, they jeopardized the project.

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