Working with legacy systems
Everything we have described so far applies to greenfield projects, for which setting up a continuous delivery pipeline is relatively simple.
Legacy systems are, however, far 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 the first step, I recommend reading a great book by Michael Feathers, Working Effectively with Legacy Code. His ideas on how to deal with testing, refactoring, and adding new features address most of the concerns about how to automate the delivery process for legacy systems.
Information
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 business decision that results in a product failure. You can read more...
