Refactoring a Filter class to leverage SOLID principles and reduce internal coupling while keeping the public class API intact

An approach to introduce an interception point in a class hierarchy to selectively execute some of the class' instances during integration tests.

Extracting new objects out of validation steps in a long method

Overview of Working Effectively with Legacy Code. What the main parts of the book are, its main ideas and some important details.

Refactoring a filesystem class to introduce tests