This document introduces Test-Driven Development (TDD), highlighting its importance in writing better code through an iterative process of designing, testing, and implementing. It covers the advantages of TDD, including shorter release cycles and improved code quality, as well as offering suggestions for getting started with TDD. Additionally, it provides references and resources for further learning about TDD and unit testing frameworks.

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