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1. Essential TDD
Bala Paranj
www.rubyplus.com

2. Outline
1. What is TDD?
2. Why TDD?
3. What are the steps in TDD?
4. Why start with a failing test?
5. How to write a failing test?

3. Outline
6. Why be minimal?!
7. How TDD separates the What from How?
8. How to get all benefits of TDD?
9. What makes TDD difficult?

4. 1. What is TDD?

5. 2. Why TDD?

6. –Kent Beck
Clean code that works gives you a chance to learn all
the lessons that the code has to teach you. If you only
slap together the first thing you think of, you never
have time to think of a second, better thing.

7. Learning

8. Better Solution

9. 3. What are the steps in TDD?

10. Step 1
Quickly add a test

11. Step 2
Run all tests and see the new one fail

12. Step 3
Make a little change to pass
the test as quickly as possible.

13. Step 4
Run all tests and see them all succeed

14. Step 5
Refactor to remove duplication

15. 4. Why start with a failing test

16. 5. How to write a failing test
• What is our System Under Test’s (SUT)
responsibility?
• What should it do?
• What is the API for making the SUT do this?
• What does the SUT need to fulfill its responsibility?
• What output are there to observe?
• How can we tell it worked correctly?

17. 6. Minimal Implementation

18. Refactor

19. Constrain

20. 7. How TDD Separates
What from How

21. API - WHAT

22. Internal Design - HOW

23. 8. How to get all Benefits of TDD

24. Discipline

25. –Kent Beck
I am not a great programmer. I am just a good
programmer with great habits.

26. 9. What makes TDD difficult

27. Summary