Working With Legacy Code - iOS TDD Workshop

Talk given on iOS TDD Workshop in Berlin.

Transcript

1. Working With Code Legacy @maciejoczko #tddberlin
2. Code is you didn’t write this morning (yet). What is LegacyCode? Code is legacy code as soon as it's written. @maciejoczko #tddberlin
3. Code is legacy code as soon as it's written. Michael Feathers, Working Effectively with Legacy Code What is LegacyCode? Code is you didn’t write this morning (yet). @maciejoczko #tddberlin
4. Code without tests* Inherited code Poorly designed code Too complicated code Illegible code *Michael Feathers What is LegacyCode? Code is legacy code as soon as it's written. Michael Feathers, Working Effectively with Legacy Code @maciejoczko #tddberlin
5. Testing scenario #1 Task @maciejoczko #tddberlin
6. How to approach it? Identify change points Find an inflection point Cover the Make changes Refactor the covered code inflection point @maciejoczko #tddberlin
7. B A D C E inflection point @maciejoczko #tddberlin
8. Violation of Single Responsibility Principle Violation of Open-Closed Principle inflection point @maciejoczko #tddberlin
9. inflection point Covering external dependencies Break @maciejoczko #tddberlin
10. inflection point Covering external dependencies internal dependencies Break Break @maciejoczko #tddberlin
11. inflection point Covering external dependencies internal dependencies Write tests Break Break @maciejoczko #tddberlin
12. inflection point Covering external dependencies internal dependencies Write tests Break Break @maciejoczko #tddberlin
13. - (NSUInteger)calculatePrice { ... StockAnalyzer *analyzer = [[StockAnalyzer alloc] init]; ... } - (id)initWithAnalyzer:(id <AnalyzerProtocol>)analyzer { self = [super init]; if (self) { _analyzer = analyzer; } return self; } external dependencies Break @maciejoczko #tddberlin
14. external dependencies Break internal dependencies Write tests Break inflection point Covering @maciejoczko #tddberlin
15. - (CGSize)calculateSize { ... UIScreen *screen = [UIScreen mainScreen]; ... } - (CGSize)calculateSize { ... UIScreen *screen = [self screen]; ... } - (UIScreen *)screen { return [UIScreen mainScreen]; } Break internal dependencies @maciejoczko #tddberlin
16. external dependencies Break internal dependencies Write tests Break inflection point Covering @maciejoczko #tddberlin
17. Write tests @maciejoczko #tddberlin
18. Make changes @maciejoczko #tddberlin
19. Testing scenario #2 Task @maciejoczko #tddberlin
20. When to Refactor? Too wide class responsibility Duplicated code Not readable code Too many method arguments (more than 2) Method has more than 20 lines Class has more than 150-200 lines @maciejoczko #tddberlin
21. Keep in mind Composition over inheritance Avoid singletons Isolate dependencies Inject dependencies @maciejoczko #tddberlin
22. Thanks! @maciejoczko #tddberlin