Peter Kofler led a coding dojo on adding tests to legacy code. The dojo focused on understanding legacy code, breaking dependencies, extracting pure functions and classes, and refactoring code to be testable. Participants worked on adding tests to the "Ugly Trivia" legacy codebase, an implementation of the game Trivial Pursuit, by extracting pure functions and classes and writing tests for the extracted code.

1. Coding Dojo:
Adding Tests to the
Ugly Trivia Legacy Code
Feb. 2014
Peter Kofler, ‘Code Cop’
@codecopkofler
www.code-cop.org
Copyright Peter Kofler, licensed under CC-BY.

2. Peter Kofler
• Ph.D. (Appl. Math.)
• Professional Software
Developer for 14 years
• “fanatic about code quality”
• I help development teams
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

3. Expectations?

4. Coding Dojo Mindset
●
Safe place outside
work
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We are here to learn
●
Need to slow down
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Focus on doing it right
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Collaborative Game
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

5. Dojo Structure
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Introduction 15'
●
Coding 60'
●
Break
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Interim (Retrospective) 15'
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Coding 60'
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Break
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Coding 60'
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Retrospective 30'
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

6. Legacy Code Skills
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Understanding Legacy Code
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Breaking Dependencies
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Bringing Code Under Test 
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Refactoring Mercilessly
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

7. Ugly Trivia
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

8. Legacy Codebase “uglytrivia“
●
Get the code
https://github.com/jbrains/trivia
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An implementation of Trivial Pursuit
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http://en.wikipedia.org/wiki/Trivial_Pursuit
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players take turns to answer trivia questions
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questions are split into categories
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players collect coins for right answers
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

9. Requirements
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Choose a testing framework
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Create tests, cover all cases
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May need to extract code to do that
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

10. Don't Focus on
Getting it Done.
F0cus on Doing
It Perfectly.

11. →Practice

12. Extract Pure Functions
●
find a piece of code that can be moved
into a separate function by using
“Extract Method“
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replace all external dependencies within
this function with independent
parameters
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add a test for that function
●
refactor the tested code as needed
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

13. Extract Class
●
isolate functionality that somehow
relates and can be separated from other
behaviour
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turn isolated methods into pure
functions
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extract these pure functions into a
separate class
●
add tests for that new class
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

14. Closing Circle
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What did you learn today?
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What surprised you today?
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What will you do
differently in the
future?
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

15. Peter Kofler
@codecopkofler
www.code-cop.org
Idea by
J.B.Rainsberger
@jbrains
https://github.com/jbrains/trivia
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

16. CC Images
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Dojo http://www.flickr.com/photos/49715404@N00/3267627038/
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Todos http://www.flickr.com/photos/kylesteeddesign/3724074594/
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Trivia http://www.flickr.com/photos/thehoneybunny/207992667/
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Wants you http://www.flickr.com/photos/shutter/105497713/
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY