The document discusses refactoring legacy code. It defines legacy code as code without tests that is difficult to understand, maintain and change. Refactoring improves code quality by making it more readable and maintainable through techniques like adding tests and breaking dependencies. Some challenges are that refactoring requires tests but tests often require refactoring first. The document recommends starting with small changes using techniques like Sprout Method to add new features as untestable code and Wrap Class to override methods in testable classes.

1. Refactoring Legacy Code
Pablo Machado
machadoum@gmail.com

2. Legacy Code?
Code written using old technology?
Code written by somebody who doesn't work
for the company anymore?
A code very fragile or complicated?

3. Legacy Code
➔ Hard to understand and maintain
➔ Intimidating to be changed

4. Legacy Code?
“To me, legacy code is simply code without tests.”
Michael Feathers

5. Legacy Code?
“If you wrote a new feature today, which took you a lot of mental
energy and time, and tomorrow you'll be afraid to change it …”

6. Refactoring?

7. Why Refactor?
➔ To understand the code
➔ To improve the health of code-base
➔ To be confident
➔ To optimize for readability

8. Why Refactor?
➔ To understand the code
➔ To improve the health of code-base
➔ To be confident
➔ To optimize for readability

10. The Fear Factor

11. Unit Test
Characterization tests

12. Refactor Dilemma
When we refactor, we should have tests.
To test we often have to refactor.

13. Legacy Code Change
Identify Change Points
Identify Test Points
Break Dependecies
Write Test
Refactor

14. Working Effectively With
Legacy Code

15. Working Effectively With
Legacy Code
Baby Steps

16. Working Effectively With
Legacy Code
Invest only where necessary

17. Working Effectively With
Legacy Code
Know how to use the tools

19. Breaking Dependencies

20. External Dependencies
Production Code

21. External Dependencies
Production Code
Test Code

22. External Dependencies
Production Code
Test Code

23. Internal/Hidden
dependencies
Production Code Refactor To Test

24. Production Code Test Code
Test Code
Internal/Hidden
dependencies

25. Refactor Technique

26. Sprout Method
When?
Add a feature as completely new code in a untestable method.
How?
Identify the inputs and outputs of the new method
Create a call for the new method
Develop the new method with TDD

27. Sprout Method
Advantages
Test new code
Separeta new cold from the old
Disadvantages
Dont test old code
Dont make the code better

28. Wrap Class
When?
Add a feature as completely new code in complex class.
How?
Create a class and extend the old class
Override the old method and make a call
Develop the new method with TDD

29. Sprout Method
Advantages
Test new code
Separeta new cold from the old
Disadvantages
Dont test old code
Dont make the code better

30. Referências
http://refactoring.com/