All we have described so far applies smoothly to greenfield projects, for which setting up a Continuous Delivery pipeline is relatively simple.
Legacy systems are, however, way more challenging because they usually depend on manual tests and manual deployment steps. In this section, we will walk through the recommended scenario to incrementally apply Continuous Delivery to a legacy system.
As a step zero, I recommend reading an excellent book by Michael Feathers, Working Effectively with Legacy Code. His ideas on how to deal with testing, refactoring, and adding new features clear most of the concerns about how to automate the delivery process for legacy systems.
For many developers, it may be tempting to completely rewrite a legacy system, rather than refactor it. While the idea is interesting from a developer's perspective, it is usually a bad...
