We share our lessons learned on how to regain control of a legacy codebase written in Java (https://github.com/xpepper/fifty-shades-of-legacy-goose-game/tree/master/goose-game-two). This codebase shows some classic design problems but more than that, badly expresses the domain of the problem we want to solve. During the session we will tackle the code the XP way: it will be a live refactoring in pair programming; we will show how the quality and expressiveness of the code can be progressively improved if we apply some good development practices with the help of some effective tools.

1. Surviving to a legacy codebase
How we take back control of legacy
codebases

2. Pietro Di Bello
@pierodibello
Paolo D’Incau
@pdincau

3. What is legacy code? 🤔

4. “Code without tests.” 🤠
Michael Feathers

5. “Valuable code that we feel afraid
to change.” 💰
J.B. Rainsberger

6. Welcome to Board Games BV…

8. Surviving principle #1: understand
the context of your software 🔦

9. The goal is not surviving, it’s
responding to business needs in a
timely manner

10. Go talk with the business

11. Start asking key questions
• “is the product already live in production?”
• “what happens if a bug slips to production?”
• “how frequently the product get released?”

12. Listen to the language of the domain

13. Where the money flows? 💶

14. Where the bugs flow? 🐛

15. The business of Board Games BV
knows that…

16. Users complain about a bug and we
are losing customers and
reputation! 💸

17. In a few weeks one of our
key gaming policies will change…

18. Let’s open the project and start
gaining confidence
(first mission: fix the bug!)

19. Surviving principle #2: maximize
safety ⛑

20. Risk vs Value

21. Change the code without breaking
anything

22. Build a safety net of
characterization tests

23. Go back to code
1. build a safety net first
2. then fix the bug!

24. Review time

25. Move carefully and take tiny steps

26. Use the IDE at its best

27. Commit as frequently as possible

28. Remember to keep the focus on
what matters 👁

29. Remember to be a good scout

30. Reduce the information overload 🤯

31. Slowly expand your sphere of
control on the codebase

32. In conclusion…

33. “The journey of a thousand miles
begins with one step.”
Lao Tzu

34. www.xpeppers.com
/xpepperssrl@xpeppers

35. Have fun with the Goose Game:
https://github.com/xpepper/fifty-shades-
of-legacy-goose-game/

36. https://goo.gl/gvu1ZK
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