TDD talk for new grad

1. Test-driven
development
Kerry Buckley
2 November 2012

2. TDD refresher

3. Towards TDD
0. manual testing
Write
Design Test Release
code

4. Towards TDD
1. automated testing
Write Write
Design Test Release
code tests

5. Towards TDD
2. test-first development
Write Write
Design Test Release
tests code

6. Towards TDD
3. test-driven development
Design
Write Run Write
test test code
Release
Run
Refactor
tests

7. Towards TDD
3. test-driven development
Red Green
Refactor

8. Beyond TDD?
4. behaviour-driven development
Executable
Customer Release
examples
Red Green
TDD
Refactor

9. Types of test

10. Acceptance tests
Test
System

11. Integrated tests
Test Test

12. Unit tests
Test Test
Mock
Mock Mock

13. Anatomy of a test
# Given some test accounts
➊ Setup account_1 = Account.new(100)
account_2 = Account.new(50)
# When I transfer money
➋ Act transfer(20, from: account_1,
to: account_2)
# Then the balances should be updated
➌ Assert account_1.balance.should eq(80)
account_2.balance.should eq(70)

14. A good test…

15. A good test…
• Expresses the programmer’s intent

16. A good test…
• Expresses the programmer’s intent
• Gives confidence that the code works

17. A good test…
• Expresses the programmer’s intent
• Gives confidence that the code works
• Only tests one thing

18. A good test…
• Expresses the programmer’s intent
• Gives confidence that the code works
• Only tests one thing
• Gives clear failure message

19. A good test…
• Expresses the programmer’s intent
• Gives confidence that the code works
• Only tests one thing
• Gives clear failure message
• Is independent of other tests

20. A good test suite…

21. A good test suite…
• Gives confidence that the system works

22. A good test suite…
• Gives confidence that the system works
• Runs quickly

23. A good test suite…
• Gives confidence that the system works
• Runs quickly
• Is well-maintained

24. A good test suite…
• Gives confidence that the system works
• Runs quickly
• Is well-maintained
• Isolates each area under test

25. Benefits of TDD

26. Benefits of TDD
• Less manual testing required

27. Benefits of TDD
• Less manual testing required
• Faster feedback

28. Benefits of TDD
• Less manual testing required
• Faster feedback
• Make it safe to change code

29. Benefits of TDD
• Less manual testing required
• Faster feedback
• Make it safe to change code
• Reduced rework and debugging

30. Benefits of TDD
• Less manual testing required
• Faster feedback
• Make it safe to change code
• Reduced rework and debugging
• Improved design

31. How do I start?

32. How do I start?
• Greenfield project? JFDI! Otherwise…

33. How do I start?
• Greenfield project? JFDI! Otherwise…
• Automate highest value tests first

34. How do I start?
• Greenfield project? JFDI! Otherwise…
• Automate highest value tests first
• Important features

35. How do I start?
• Greenfield project? JFDI! Otherwise…
• Automate highest value tests first
• Important features
• Where the most bugs occur

36. How do I start?
• Greenfield project? JFDI! Otherwise…
• Automate highest value tests first
• Important features
• Where the most bugs occur
• Use TDD for new features

37. How do I start?
• Greenfield project? JFDI! Otherwise…
• Automate highest value tests first
• Important features
• Where the most bugs occur
• Use TDD for new features
• Add tests for bugs when they’re found

38. Further reading