The document describes a Global Day of CodeRetreat event taking place in Munich on November 18, 2017. The event involves 2000 developers from 100 cities and 6 continents pairing up to work through 6 sessions of test-driven development (TDD) exercises over 1 day using 1 kata (problem). Each session involves switching pairing partners and introduces constraints to challenge participants, such as writing tests first, continuous integration/refactoring, object-oriented principles, and functional programming techniques. The goal is for developers to learn and improve their TDD and software design skills in a low-pressure environment away from their day jobs.

1. GLOBAL DAY OF
CODERETREAT
Munich,
November 18, 2017

2. @DAVIDVOELKEL
@codecentric
@softwerkskammer
#TDD

3. WHAT IS A CODERETREAT?

4. 1 DAY
1 KATA

5. 1 DAY
1 KATA
6 SESSIONS
6 PAIRING PARTNER
6 CONSTRAINTS

6. Hidden Slide Slower
2000 Developers
100 Cities
6 Continents
18 Time zones
GLOBAL DAY OF
CODERETREAT

7. ROLES
HOST
&Z?jBrA+>y(r

8. ROLES
HOST
FACILITATOR
&Z?jBrA+>y(r

9. ROLES
HOST
FACILITATOR
&Z?jBrA+>y(r
YOUR PAIR

10. ROLES
HOST
FACILITATOR
&Z?jBrA+>y(r
YOUR PAIR
YOU

11. WHY A CODERETREAT?

12. @ DAY JOB

13. @ DAY JOB
NO ROOM FOR
LEARNING &
IMPROVEMENT

14. A SAFE PLACE
NO TIME PRESSURE

15. A SAFE PLACE
NO TIME PRESSURE
BE RESPECTFUL

16. GOALS
FUN

17. GOALS
FUN
LEARN

18. CHALLENGE YOURSELF
Experiment
Stretch your
comfort zone
Learn new practices

19. FOCUS ON
finish the problem
doing it right
practicing
improvement

20. DELETE YOUR CODE
After each session

21. WHY RESET?
Clear your mind
Focus on different goals
Get to the same level

22. ORGA

23. PREREQUISITES
Coding Environment
Testing Framework
VCS (e.g. Git, Mercurial)

24. Local Sponsors
Hidden Slide Slower

25. PLEASE
Ask for help
Use the feedback wall
=>

26. AGENDA
Intro
Session 1-3
Lunch
Session 4-6
Closing Circle / Retro

27. KATA
TIC TAC TOE
3x3 Board
Player "X" and "O"
Player with 3 in one line wins
• horizontal
• vertical
• diagonal

28. SESSION 1 PART 1
"THE TEST LIST"
Goal
Understand
• the problem
• its test cases

29. SESSION 1 PART 1
"THE TEST LIST"
Collect a list of tests in a text file
(no coding yet!)

30. SESSION 1 PART 1
"THE TEST LIST"
Collect a list of tests in a text file
Player with 3 in one line wins
• horizontal
• vertical
• diagonal

31. SESSION 1 PART 1
"THE TEST LIST"
Sync
What tests do you have? Names?
Test categories? Dimensions?
Combinatorics?

32. SESSION 1 PART 2
"TEST FIRST"
Write a test and let it fail
Write the simplest possible
implementation that the test runs green

33. SESSION 1 PART 2
"TEST FIRST"
Why?
Set a clear goal
no YAGNI
Separate API from Implementation
Causality: Red->Green
Testing discipline, high coverage
early ROI

34. SESSION 1 PART 2
"TEST FIRST"
Write several tests and let them fail

35. SESSION 1 PART 2
"TEST FIRST"
Sync
Which tests did you write? Naming?
Object under Test?
Representation of Fields?

36. PLEASE LINE UP!
HOW IS YOUR EXPERIENCE
LEVEL WITH TDD?

37. SESSION 2
"TDD + PING PONG"
GOALS
Learn TDD
Change pairing roles often

38. SESSION 2
"TDD + PING PONG"
TDD
= test-first + refactoring
= red, green, refactor

39. SESSION 2
"TDD + PING PONG"
Focus
write test: what should code do
implement: solve the problem
refactor: good design

40. SESSION 2
"TDD + PING PONG"
Uncle Bob’s 3 Rules of TDD
1. You can't write any production code until you
have first written a failing unit test.
2. You can't write more of a unit test than is
sufficient to fail, and not compiling is failing.
3. You can't write more production code than is
sufficient to pass the currently failing unit test.

41. SESSION 2
"TDD + PING PONG"
TDD GOALS
Incremental & Clean Design
Fast Feedback

42. SESSION 2
"TDD + PING PONG"
Ping Pong Pairing
1. Alice writes failing test
2. Bob makes test green
3. Bob writes failing test
4. Alice makes test green
5. Alice writes failing test
6. …

43. SESSION 2
"TDD + PING PONG"
Uncle Bob’s 3 Rules of TDD
1. You can't write any production code until you
have first written a failing unit test.
2. You can't write more of a unit test than is
sufficient to fail, and not compiling is failing.
3. You can't write more production code than is
sufficient to pass the currently failing unit test.
Do refactor duplication and improve names

44. SESSION 2
"TDD + PING PONG"
Sync
What did you observe?
What did (not) work?
What about design/refactoring?
How did pairing work?

45. SESSION 3
"BABY STEPS TDD"
LEARNING GOALS
Why are baby steps important
How to achieve baby steps

46. SESSION 3
"BABY STEPS TDD"
change 1
Initial code state
change 2
state 1
state 2
…
change n
target code state
● slow feedback
● high risk
● exponential complexity
● problems hard to find
LEAP

47. SESSION 3
"BABY STEPS TDD"
get green asap
● commit on green
● revert to green
change 1
Initial state
change 2
state 1
state 2
…
change n
target state
BABY STEPS

48. SESSION 3
"BABY STEPS TDD"
+ fast feedback
+ less risk
- a bit more effort
change 1
Initial state
change 2
state 1
state 2
…
change n
target state
BABY STEPS

49. SESSION 3
"BABY STEPS TDD"
Start a 2 min. timer when you get red
When back to green reset the timer and
When timer rings and you are still in red
git reset --hard
git commit

50. SESSION 3
"BABY STEPS TDD"
Sync
Did you get better during the session?
How did it work, was it hard?
How did you achieve baby steps?

51. SESSION 4
"CLEAN CODE"
GOALS
Readable Code
Maintainable Code

52. SESSION 4
"CLEAN CODE"
Clean Code constraints
"Code Swap" at the end

53. SESSION 4
"CLEAN CODE"
Constraints
Use good names
No duplication > 2 times
Single Responsibility
Max 4 LOC / method

54. SESSION 4
"CLEAN CODE"
Why?
Use good names
No duplication > 2 times
Single Responsibility
Max 4 LOC / method

55. SESSION 4
"CLEAN CODE"
Code Swap
review
• 5 min by other team
• write comments
read comments

56. SESSION 4
"CLEAN CODE"
Sync
What was hard?
What violations did you see?

57. SESSION 5
"OOP"
GOAL
Rethink good Object Oriented Design

58. SESSION 5
"OOP"
What makes
good OO Design?

59. SESSION 5
"OOP"
Constraints
Wrap all primitives and strings
Use first-class collections
Use only one dot per line
Keep all entities small
No more than two instance variables
Don’t use any getters / setters / properties

60. SESSION 5
"OOP"
Why?
Wrap all primitives and strings
Use first-class collections
Use only one dot per line
Keep all entities small
No more than two instance variables
Don’t use any getters / setters / properties

61. SESSION 5
"OOP"
Constraints
Wrap all primitives and strings
Use first-class collections
Use only one dot per line
Keep all entities small
No more than two instance variables
Don’t use any getters / setters / properties

62. SESSION 5
"OOP"
Sync
• What was hard?
• How did you handle it?
• Which constraints make sense
for "real life"

63. SESSION 6
"FAVORITE"
The goal is fun!

64. SESSION 6
"FAVORITE"
Choose yourself
Your favorite of the day
No conditionals and/or loops
Wishful thinking (Outside-In)
Functional Calisthenics
…

65. Sync
• What did you choose?
• What was hard?
• How did you handle it?
SESSION 6
"FAVORITE"

66. • what did you learn today?
• what surprised you about today?
• what are you going to do differently
in your Project?
CLOSING

67. LICENSE
Creative Commons Attribution-ShareAlike

68. IMAGES
Some are Public Domain except theses licensed with
Creative Commons with attributions:
By Symbolon
By Ainsley Wagoner

69. IMAGES
By Luis Prado
Dave Gandy
Christopher.Michel

70. IMAGES
Kigsz
Another Believer
Maria Ly

71. IMAGES
Büşra ÖZCOŞKUN
Guru
Aneeque Ahmed

72. IMAGES
Rudy Jaspers
logan
Hopkins

73. IMAGES
Kick
THOR
Seattle Municipal Archives

74. IMAGES
Uriel Sosa
Adrien Coquet
Yogesh More