Integrating tools and automation

Throughout this book, we've discussed the importance of testing a couple of times. DevOps advocates testing at every single stage in the life cycle, from development to deployment. This includes security testing. But how can we achieve this continuous integration? The goal is to have tests running at developer check-in, while they pull code from repositories, during the builds, and during the actual deployments, including staging.

Let's look at continuous integration (CI) first. Developers will frequently do check-ins on code; in some cases, this can be up to several builds per day. That's the aim of CI and the agile way of working in DevOps: developers don't work on huge programs anymore; instead, they apply small iterations of code builds, adding one feature at a time. This way, it's easier to track changes in the code and, importantly, roll back if the addition is causing failures.

CI is about integrating these changes...