Tips on how to deal with legacy code, techniques and patterns. Including stuffs from Adam Tornhill, Michel Feathers, Simon Brown and Dan North. From presentation at Websteps Kompetensbio November 2015.

1. Tackling legacy code
Making scary code less scary
Tangled Fishing Line - Aristocrats-hat https://flic.kr/p/6qdTC1 CC BY 2.0

2. Tomas Malmsten
Software Craftsman
@tomasmalmsten
http://www.tomasmalmsten.com
public@tomasmalmsten.com
Founder of
@oescg
Programmer at
Øresund Software
Craftsmanship Group

3. What?
“Any code I didn’t write”
“Any code not covered by test”
“Any code older then n years”
“Any code that is hard to understand”
“Legacy code is all production code which scares you when
you have to change it.”

4. “All code required to deliver the business capability of the
system ”
Production code?

5. Why?
Fix problems
Introduce new features
Achieve

6. 1. What do we want to achieve?
2. Where do we start?
3. What is this code doing anyway?
4. How can I keep safe?
5. Next steps

7. Ambition Level
Achieve

8. Where do we start then?

9. Start where you
stand
.
Where do we start?
Leaning - Tom Parkinson - https://flic.kr/p/6esPpL - CC BY 2

10. Where do we start?

11. Offender profiling
Where do we start?
Prague Photographic Hotspot - Steven Kay - https://flic.kr/p/9e4vHH - CC BY-SA 2.0

12. Temporal
Coupling
Where do we start?

13. What is this code doing
anyway?
From IOCCC 2013 winners cable3 - 8086tiny by Adrian Cable

14. Specification tests
Understanding code
Design - Ben Brown - https://flic.kr/p/8aK8Wh - CC BY-SA 2.0

15. From The Cucumber for Java Book by Seb Rose, Matt Wynne,
Aslak Hellesøy

16. Tooling
Cucumber
SpecFlow
RSpec
Selenium support
KarmaJS
but basically any BDD tool works

18. Conversational
Scrutiny
Understanding code
Jennifer Drawing Ideas - Juhan Sonin - https://flic.kr/p/juPL2q - CC BY 2.0

19. Telling the story of the system
Understanding code

20. Understanding code

21. C4 Architecture Diagrams
Context
Container
Component
Class
Understanding code

22. Tangled Fishing Line - Aristocrats-hat https://flic.kr/p/6qdTC1 CC BY 2.0

23. The Golden Master
NeXTSTEP 3.3 Gamma (Golden Master) - Gerben Wierda- https://flic.kr/p/7rF8jj - CC BY-SA 2.0
How to proceed

24. Light the Forest
How to proceed

25. Find the seams
How to proceed

26. Code from: https://github.com/sandromancuso/trip-service-kata

28. Break dependencies
How to proceed
Tama Leaver - https://flic.kr/p/dXgorH - CC BY 2.0The Enterprise Dependency - http://thedailywtf.com/articles/The-Enterprise-Dependency

29. Name everything
How to proceed

30. Next steps

31. Find out what the team knows
Domain
Languages
Testing
Automation
Frameworks
Next steps

32. Start small
Small changes
Small tests
Small incremental learning
Next steps

33. Employ continuous learning
Daily standup with a learning focus
Coder dojos
Mob programming
Pair programming
Retrospective
Next steps

35. Summary
Legacy code =
All production code which scares you when you have to change it.
Why
Ambition level
Where to start
Where you stand
Hotspot Analysis
Temporal Coupling Analysis

36. Summary
How to understand
Specification Tests
Conversational Scrutiny
Telling the story of the system
C4 Architecture Diagrams

37. Summary
How to proceed
Golden Master
Light the Forest
Find the seams
Break dependencies
Name everything

38. Next steps
What does the team know
Start small
Optimise for learning

39. Tomas Malmsten
@tomasmalmsten
http://www.tomasmalmsten.com
public@tomasmalmsten.com
http://www.slideshare.net/TomasMalmsten/tackling-legacy-code-november-2015
Øresund Software
Craftsmanship Group
@oescg
http://www.efolder.net