Rescuing Legacy Code by Extracting Pure Functions. Come across strange, pre-existing code. Decide you need to change it. Follow the pattern described herein. Apply TDD afterwards. I so wish someone had shown me this technique years and years ago. Also, Composed Method (from Smalltalk Best Practice Patterns) is so great, I can't even put it into words.
Changing legacy code, made less painful
Adam Keys
@therealadam