This document discusses Behavior Driven Development (BDD) as an evolution of Test Driven Development (TDD) that focuses on writing specifications and documentation in a user-centric way. BDD helps developers understand where and what to test by focusing tests around user stories and specifying behaviors for different contexts rather than just asserting outcomes. Examples are given demonstrating how to write BDD specifications for a Stack data structure focusing on behaviors for different contexts like an empty stack or full stack. Tools for implementing BDD with languages like JBehave, JDave, and Instinct are also mentioned.

1. Behavior Driven
Development
Chun-Wen Wang
Aug 21, 2007

2. Background

3. TDD

4. Test Driven
Development

6. Problem

7. Developers don’t know ...
• where to start
• what to test
• what not to test
• how much to test in one go
• what to call tests
• how to fix a broken test
• that TDD is about design

8. Test?

9. Assert?

10. Sapir-Whorf
hypothesis

12. BDD

13. Behavior Driven Development
• It’s about writing specifications
• It’s about writing how the code works
• It’s about understanding how the system
works
• It’s about understanding what I have to write

14. BDD helps you realize
• •
where to start outside-in
• •
what to test user stories
• •
what not to test anything else
• •
how much to test in one go as little as possible
• •
what to call tests intent
• •
how to fix a broken test documentation
• •
that TDD is about design ......?!

15. Behavior
• The actions or reactions of an object or
organism, usually in relation to the
environment. -- Wikipedia
• Anything that an organism does involving
action and response to stimulation. --
Merriam-Webster

16. Example: Stack
• Stack
• as empty stack, ....
• as full Stack, ....
• neither empty nor full, ....

17. Example: Stack
• Specification
Stack
• as empty stack, ....
• as full Stack, ....
• neither empty nor full, ....

18. Example: Stack
• Stack Context
• as empty stack, ....
• as full Stack, ....
• neither empty nor full, ....

19. Example: Stack
• Stack
• as empty stack, .... Behavior
• as full Stack, ....
• neither empty nor full, ....

20. Behavior of Empty Stack
• Empty stack
• is empty
• is no longer empty after push
• ...

21. Behavior of Empty Stack
• Empty stack Context
• is empty Behavior
• is no longer empty after push
• ...

22. How to Do It?
• JBehave - 1.0.1
• http://jbehave.org/
• JDave - 0.9.0
• http://www.jdave.org/
• Instinct - 0.1.4
• http://code.google.com/p/instinct/

23. Example (JDave)

24. < >

25. Example using RSpec

26. </ >

27. Further More

28. Discussed Not yet
Module
Under Test

29. Mock Objects

30. ... aren’t Stubs

31. To be continued...

32. Q &A