Refactoring legacy code
2 likes806 views
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.
Refactoring legacy code
- 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
- 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
- 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