Test Driven Development in the context of Legacy Code. Workshop for the Toronto Test Driven Development Meetup.

1. Test Driving Legacy Code
Breaking out of the “Legacy Code Dilemma”

2. About me…
Developer since 1994
(C++ used to be my friend…)
Agile Coach since 2009
fernando.a.cuenca@gmail.com
@fer_cuenca

3. Big Thanks to our
Sponsor!
http://digitalfactory.scotiabank.com

4. Agenda
TDD in the context of Legacy Code
Practice Session 1 + Debrief
BREAK
Practice Session 2 + Debrief

5. So, what is “Legacy Code”
anyways?

6. Code that
actively prevents
you from making
changes
Code we’re
afraid to change
Code where the
design makes
more design
decisions than
the programmer
Code without
Unit Tests

7. you could
have a
“magic
button”…
Pecha Kucha @ OOP 2015 "Is TDD dead?
https://www.youtube.com/watch?v=9NANcPTbDBQ

8. Start
Here
TDD
Write a
failing
test
Make it
pass
Improve
the
Design

9. The Legacy Code Dilemma
Michael Feathers
“Working Effectively with Legacy Code”

10. Pinning Down
Behaviour

11. Your turn now!
2 Practice sessions + Debrief
We need to choose a common Programming
Language
Java
C#
Javascript
Find a partner (we’ll switch for Session 2)
Log in to my Cyber-Dojo:
http://cyberdojo.ddns.net

12. Welcome to Ugly Trivia!
What does the code do?
What are the different RESPONSIBILITIES?
How “good” or “bad” is this code? Why?
How much “Technical Debt” does it have?
Can you identify two distinct kinds of tests?
What is the purpose of each?

13. Key Ideas

14. Adding More Characterization
Tests
What kinds of things are displayed? When?
What’s the minimum number of players?
What happens when a player rolls?
How does the current location change?
How are categories selected?
How are coins awarded?
What’s the order of the players?
How big is the board? How is it traversed?
What happens when the answer is correct?
Incorrect?
What are the rules around the “penalty box”?

15. Debrief: What was it like?
What are most important insights you gained
from the session?
What was helpful / not-helpful?
What will you do differently in the next session?

16. Let’s fix some defects!
Fix typo when answering correctly ("Answer was
corrent")
Terminate nicely instead of throwing exceptions:
when questions run out
when rolling before adding players

17. Let’s add some new
features!
Backlog
1. Display the winner's
name when the game
ends
2. Display output in
multiple languages
Guidelines
Cover, then modify
Can you test-drive a
replacement?
Are your tests passing
all the time?
How small are your
steps? Can you make
them smaller?

18. Large-Scale Refactoring
New Features
1. Configurable board size
2. New Category: Politics
3. When questions run out (in
any category), the game ends
and the player with the most
coins wins
4. Different categories pay
different amount of coins
when answered correctly
5. if 2 people in a row answer
incorrectly, the order of
players inverts
Guidelines
Pick a feature to work
on
Agree on a “good
design” for it.
Sketch general
incremental steps to
get there

19. The Mikado Method (https://mikadomethod.wordpress.com)

20. Debrief: What was it like?
What are most important insights you gained
from this session?
What was the overall feeling?
How does the result compares to what you
initially thought the outcome might be?
How/Where could this approach be useful?
What will you do differently tomorrow, back in the
office?

21. Learning more

22. Thank you!
And please, complete the feedback forms!!