Doing Code Katas alone or in a Dojo can help sharpen our elementary skills as software developers. Practicing IDE shortcuts and TDD mini-step cycles is very useful for the daily business, yet I find some existing Code Katas too far away from real-life programming situations. That’s why I came up with the Trading Card Game Kata – which is (very loosely) based on Blizzard Entertainment’s free-to-play online-game “Hearthstone – Heroes of Warcraft”. This Kata is focused on practicing TDD in a slightly more complex (but not complicated) situation where you might have to think about rules like Single Responsibility Principle or Command Query Separation and might even feel the urge to use a Mocking framework at some point. The rules are kept very simple to begin with but can be extended easily to make the Kata more challenging or concentrate on specific aspects of software development. In this talk I will first introduce the ideas of Katas in general and explain the TCG Kata rules to you. Then I will present some real-life best practices for writing good developer tests, using my TCG Kata sample solutions as a showcase. This will include: * Picking the right Test Double * Test Data Builders * Behavior Tests with BDDMockito * Prose-like Assertions with Hamcrest * Readability Sugar * Custom Matchers against Test Diabetes The full Kata ruleset and sample solutions in Java 8 (JUnit4, Mockito, Hamcrest) and Groovy (Spock) can be found on https://github.com/bkimminich/kata-tcg. A recording of this talk at „Agile Saturday X“ in Tallinn, Estonia can be found on https://vimeo.com/92886146.

1. Practicing Advanced
Unit Testing
v2.3.2 (17.09.2014)
withthe
«Trading Card Game»
Kata
Battlecry: Draw a slide.
Deathrattle: Transform
audience into 1/1 sheep.
Speaker

2. Kata
Kata (型or 形literally: "form”) is
a Japanese word describing detailed
choreographed patterns of movements
practiced either solo or in pairs.

3. Trading Card Game (TCG)
A […] trading card game (TCG) […] is
a card game that uses specially
designed sets of playing cards […]
mass-produced for trading or
collectibility, and it must have rules
for strategic game play. Acquiring
these cards may be done by trading
with other players or buying card
packs.

4. Why invent another Kata?
Bro, why U not use
?????
Rules not
extensible
Not TDD-friendly
Too easy

5. Hearthstone: Heroes ofWarcraft®

6. Kata Trading Card Game

7. Player Setup
Health Mana
30 0/0
0 0 1 2 2 2 3 3
3 4 4 4 5 6 6 7 8
Deck
1 3
5
Hand

8. Cause
1 Damage
30 0/0 30
2
7
Active
Player
1 3 5
8
01//11
Gameplay
2
3
Play Card 1
29
0/0
Draw Card
-1
Receive +1
Replenish Mana Slot
Mana
Pay 1
Mana
Game
Table
Draw extra
Card

9. Forced Turn Skip
0/1
30 1/1
29
5 8 2
3 2
2 4
3
No affordable
Cards
2/2
7

10. 2/-2
29
27
4
Ongoing Gameplay
0/2
30 1/1
5 8 2
3 2
3 4
2
2
7

11. 12
4
Overload Rule
8/8
18 7/7
5 8 7
6 1 0 8
2
Discard Card
when Hand
already holds
5 Cards 7

12. Mana Cap
10/10 4
5
8 10/10
6 Mana is 6 1
capped at
10 Slots

13. Bleedout Rule
Cause
1 Damage
10/10 4
5
8 10/10
Drawing
from empty
6 6 1
Deck
7-1

14. Game End
10/10 4
5
4/10
7 10/10
--62
6 6 1
Winner! Loser!

15. Kata TCG Rules & Variations
https://github.com/bkimminich/kata-tcg
Detailed rules description
Advanced Variations
Healing cards
Use cards as Minions
Different cost & damage
Card drawer cards
Deck customization

16. Kata TCG Sample Solution in Java
https://github.com/bkimminich/kata-tcg
Java 8
Lambdas & Stream API
Junit
Mockito
For handling dependencies of tested objects
Hamcrest
Matchers for better legibility in assertions
System Rules
JUnit@Rules for substituting java.lang.System

17. Other Sample Solutions
https://github.com/bkimminich/kata-tcg
Groovy
Spock
JavaScript
Karma
Jasmine
PhantomJS

18. Advanced Unit Testing
Examples

19. Skip No-Brainers
…
Compile Error
as Red Test
Red
Refactor Green

20. Obvious Implementation
Simplest
possible step
Simplest
useful step

21. Specify theObject under Test
Irrelevant
Details
Setter introduced
for testing
Implementation
Detail
Assuming
Hidden Default

22. Define theObject under Test
Another unwanted
setter
Hidden default
problem solved

23. Builder Pattern
Reads like natural
language
Explicitly listed
Expectations
No unnecessary
details
…?

24. Builder Internals
Sensible
Default Values
Package visible full
Constructor needed

25. Fluent API
Setting properties
via fluent API

26. Mocking Behavior
Interface has no
implementation yet
Mock Behavior
for this Test

27. Trashcan Refactoring
CardPicker turned out
to be overengineered
Mocking

28. Mocking BDD Style
Can be
confused with
Given-When-Then
part
Can be
confused with
Given-When-Then
part

29. Mocking BDD Style
Sugar coating
for BDD syntax
Matches its meaning in
Given-When-Then structure

30. Avoid Redundancy
Redundant & spoiled with
Implementation Details
Another slight
redundancy

31. Avoid Constants
Disturbs the
reading flow

32. Syntactic Sugar
Improves
Legibility and
removes
Redundancy

33. More Syntactic Sugar
Magic
Numbers Different Level of
Abstraction

34. Syntactic Artificial Sweetener
No-Op
Syntactic
Sugar for
Legibility
Syntactic
Sugar reduces
Redundancy

35. Test Diabetes
Too much Sugar is
bad for your Test
Customer Matchers
can medicate this

36. Custom Matcher
Encapsulation of
Expectation
Produces helpful
Error Messages
Even better
with just a little
bit of Sugar

37. Demo | Q&A

38. Demo: Test Execution
Pretty fast All tests pass

39. Demo: Code Coverage

40. UglUygRleytUroI UI
Demo: Human vs. AI Game
Player Input
via System.in
AI beats me!
Again! 

41. Thank you for your attention!
Recording of this talkat „Agile SaturdayX“ in Tallinn, Estonia
https://vimeo.com/92886146
https://twitter.com/bkimminich
https://linkedin.com/in/bkimminich
https://google.com/+BjörnKimminich
http://slideshare.net/BjrnKimminich/

42. Credits
Background Image: Demonplay (Permission of use granted)
Other Images:
Blizzard Entertainment (Permission of use requested)
Wikipedia, Github, Agile Estonia
Allmystery.de, Gueball.de, Natekohl.net, Scenicreflections.com
Hearthstone: Heroes of Warcraft® is a trademark or registered trademark of
Blizzard Entertainment, Inc., in the U.S. and/or other countries.