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Legacy Code Hands-on Session
The document discusses strategies for testing and refactoring legacy code, particularly in the context of a social networking site for travelers. It emphasizes the importance of maintaining test coverage before modifying production code and offers practical tips for effectively refactoring. Key takeaways include starting refactoring from the deepest branches, committing improvements frequently, and ensuring code remains readable and maintainable.
Legacy Code Hands-on Session
- 1. Testing and Refactoring Legacy Code Sandro Mancuso @sandromancuso craftedsw.blogspot.com
- 2. What is thissession about?
- 3. Business Requirements Imagine asocial networking website for travellers • You need to be logged in to see the content • You need to be a friend to see someone else’s trips
- 4. Legacy Code Rules •You cannot change production code if not covered by tests – Just automated refactorings (via IDEs) are allowed, if needed to write the test
- 5. Tips • Use acode coverage tool • Commit as often as possible – Enables you to commit (push) improvements quickly – Allows you to roll back (reset) if you get lost • When refactoring, try to stay in the green for as long as possible
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- 7. Working with LegacyCode Tips Start refactoring from deepest to shortest branch Start testing from shortest to deepest branch
- 8. Trip Service -Problems <<Singleton>> UserSession +getInstance() : UserSession +getLoggedUser() : User TripService +findTripsByUser(User) : List<Trip> TripDAO +findTripsByUser(User) : List<Trip>
- 9. Legacy Code CommonProblems • Hard-wired dependencies – Create a “seam” to break dependencies • Extract dependency in a protected method • In our test, extend the class under test and override the method with the dependency so you can mock the result • Identify feature envy – Move behaviour out to the appropriate class
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- 11. Remember Start refactoring from deepest to shortest branch Start testing from shortest to deepest branch
- 12. Refactoring vs Re-design •After localised refactoring, consider fixing the design • Writing tests for existing code may perpetuate a bad design
- 13. Craftsmen at work •Write readable and maintainable code – Code must express business rules • Strive for simplicity • Know your tools well (i.e. frameworks, shortcuts) • Work in small and safe increments – Commit often • Embrace changes, be brave • Boy scout rule / No broken windows
- 14. Thanks https://github.com/sandromancuso/trip-service-kata Sandro Mancuso @sandromancuso craftedsw.blogspot.com