This is the slides of my talk @ Taiwan Java User Group on 2011/07/09. You can watch the video here (in Chinese): http://vimeo.com/26538602

1. Introduction to
Test-Driven Development
Hao-Cheng Lee
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2. About me
● Hao-Cheng Lee
● Java Engineer for 7+ years
● Software Engineer @ Armorize
● Interested in Java, Scala, TDD, CI
● email: haocheng.lee@gmail.com
● twitter: haocheng
● Google+: 浩誠

3. Download Java 7 RC Now
Project Coin Slides

4. Agenda
● What is TDD?
● Why use TDD?
● How to do TDD?
● Pros and Cons
● How do I start?

5. TDD
=
TFD
+
Refactoring

7. Not about
writing tests...

8. TDD is about
writing better
code

9. from http://ch.englishbaby.com/forum/LifeTalk/thread/441379

10. Test Myths

11. I have no time
for testing

12. Technical Debt
from http://www.freedebtadvice-uk.com/

13. My code is
BUG-FREE!

14. from http://vincentshy.pixnet.net/blog/post/5397455

15. QA will do the
testing

16. Black Box Testing
from http://www.jasonser.com/marketing-black-box/

17. http://www.ocoee.org/Departments/HR/

18. Faster
from http://cllctr.com/view/c2fdb4d2625e109069c843ea1bb99e50

19. from Test Driven Development Tutorial by Kirrily Robert

20. Faster
● Shorter release cycle
● Automation saves time
● Find bugs earlier

21. Better
from http://www.nataliedee.com/archives/2005/sep/

22. Better
● Greater code coverage
● The courage to refactor
● Prevent regression bugs
● Improve your design

23. "I'm not a great programmer;
I'm just a good programmer
with great habits."
- Kent Beck

24. Testing the Old Way

25. TDD

26. TDD

27. How to do TDD?
● Design: figure out what you want to do
● Test: write a test to express the design
○ It should FAIL
● Implement: write the code
● Test again
○ It should PASS

28. Design
We need a method add(), which
takes two parameters and add
them together, then it will return
the result.

29. Test

30. FAIL
java.lang.AssertionError: expected:<2> but was:<0>
...
at tw.idv.haocheng.play.
CalculatorTest.one_plus_one_is_two
(CalculatorTest.java:20)

31. Implement

32. PASS

33. Write the least code
to make the test pass

34. More Test

35. FAIL
java.lang.AssertionError: expected:<4> but was:<2>
...
at tw.idv.haocheng.play.
CalculatorTest.two_plus_two_is_four
(CalculatorTest.java:25)

36. Implement

37. PASS

38. Design
The add() method only accept
positive numbers

39. Test

40. FAIL
java.lang.AssertionError: IllegalArgumentException expected
at org.junit.Assert.fail(Assert.java:91)
at tw.idv.haocheng.play.
CalculatorTest.negative_numbers_will_throw_exception
(CalculatorTest.java:32)

41. Implement

42. PASS

43. from http://www.oracle.com/

44. Design
We need a addNewCustomer()
method that will save a customer
record in Database

45. Test

46. Test

47. FAIL
java.lang.NullPointerException
at tw.idv.haocheng.CustomerDAOTest.addNewCustomer
(CustomerDAOTest.java:24)

48. Implement

49. PASS

50. from https://www.google.com/accounts/NewAccount

51. Design
We hava a page that user
can apply for a new account

52. Test

53. Test

54. FAIL
wicket.markup.MarkupException: Unable to find
component with id 'accountFormPanel' in
[MarkupContainer ....
at ngc.account.wicket.edit.CreateAccountPageTest.
setUp
(CreateAccountPageTest.java:49)

55. Implement

56. PASS

57. Unit Test Frameworks
● Java - JUnit
● Python - PyUnit
● PHP - PHPUnit
● Ruby - Test:Unit
● Javascript - Jasmine
● .Net - NUnit

58. There's No Silver Bullet
from http://www.penn-olson.com/2009/12/22/social-media-the-silver-bullet/

59. Costs
from http://ora-pl-sql.blogspot.com/2011/05/database-costs.html

60. It takes time...
from http://chunkeat626.blogspot.com/2010_11_01_archive.html

61. Need to
maintain tests

62. TDD is not suitable for...
from http://www.flickr.com/photos/ilike/2443295369/

63. from http://tw.gamelet.com/game.do?code=heroes

64. from http://dilbert.com/

65. But how do I start??
from http://zekjevets.blogspot.com/2010/02/alternative-racism.html

66. from http://www.alexbolboaca.ro/wordpress/the-remote-pair-programming-tour

67. Suggestions
● Prepare tools and environments
● Learn to write Unit test
● Start from easy ones

69. Reading List
● The Bowling Game Kata
● Unit Testing Guidelines
● Why are we embarrassed to admit that we don’t know how
to write tests? (中譯版本)
● "The Clean Code Talks -- Unit Testing"
● Top 10 things which make your code hard to test

70. References - Test-Driven Development
● Test Driven Development Tutorial by Kirrily Robert
● Engineer Notebook: An Extreme Programming Episode by
Robert C. Martin and Robert S. Koss
● Technical Debt by Martin Fowler
● InfoQ: Testing Misconceptions by Liam O'Connor
● Unit Test Isolation
● Erratic Test
● Singletons are Evil
● RSpec 讓你愛上寫測試