Working Effectively with Legacy Code

Chapter 25: Dependency-Breaking Techniques

In this chapter, I’ve written up a set of dependency-breaking techniques. This list is not exhaustive; these are just some techniques that I’ve used with teams to decouple classes well enough to get them under test. Technically, these techniques are refactorings—each of them preserves behavior. But unlike most refactorings written up in the industry so far, these refactorings are intended to be done without tests, to get tests in place. In most cases, if you follow the steps carefully, the chance of mistakes is small. This doesn’t mean that they are completely safe. It is still possible to make mistakes when you perform them, so you should exercise care when you use them. Before you use these refactorings, ...