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Php day2010
- 1. Architettura e testabilità (Architecture and testability) Listen to your tests on steroids Giorgio Sironi
- 2. Who am I ● PHP freelancer from 2005 ● Writer for php|architect, DZone ● Perito informatico, undergraduate in Engineering at Politecnico di Milano
- 3. This talk ● Maintainability, and why testing ● Various techniques to favor ease of testing AND maintainability ● Slides in English (test d'unità, Legge di Demetra...)
- 4. Other talks ● Dependency Injection ● Testare l'ignoto ● Agile software lifecycle
- 5. What is maintainability? ● Being ready to change! …but not too much ● Taking the first bullet
- 6. Favored by maintainability ● New requirements ● Evolving requirements ● Iterative development ● Long-term maintenance
- 7. Kinds of tests ● Unit tests ● Integration tests ● Acceptance (end-to-end) tests and functional tests
- 8. Maintainability (1 of 2) SOLID principles (not all of them) ● Single responsibility ● Open/closed ● Dependency Inversion
- 9. Maintainability (2 of 2) Loose coupling High cohesion Information hiding Orthogonality ...needed from day 1, like readability and testability
- 10. Good but... Good buzzwords, but how do I apply that in practice?
- 11. Testing first ● Testing first → Testable code ● Testable code → Maintainable code
- 12. Problems with tests ● A test is slow? ● A test is brittle? ● A test is difficult to write?
- 13. Solution to problems with tests Change the design to ease testing (listen to your tests)
- 14. Test must change too ● Good: test suite ● Bad: no test suite ● Worse: unmaintainable test suite
- 15. Examples of listening to the tests ● Small tests => high cohesion ● Unit tests => loose coupling 4 pillars...
- 16. 1. Dependency injection ● No new operator outside of Factories ● Easy to change lifecycles and implementations
- 17. 1. Dependency Injection (without) <?php class Ferrari { private $_engine; public function __construct() { $this->_engine = new Engine(); } }
- 18. 1. Dependency Injection (with) <?php class Ferrari { private $_engine; public function __construct(Engine $engine) { $this->_engine = $engine; } }
- 19. 2. Avoid static methods ● Explicit concept ● Orthogonality
- 20. 2. Avoid static methods (before) <?php class Collection { public function find($key) { Sorter::sort($this); // ..search stuff } }
- 21. 2. Avoid using static methods (after) <?php class Collection { public function find($key) { $this->_sorter->sort($this); // ..search stuff } }
- 22. 3. Law of Demeter ● Do not walk the... arrows ● Exceptions: Factories, data structures
- 23. 3. Law of Demeter (without) <?php class PC { public function powerOn() { $this->_mobo->cpu->cache ->powerOn(); } }
- 24. 3. Law of Demeter (with) <?php class PC { public function powerOn() { foreach ($this->_powered as $item) { /** @var Powered $item */ $item->powerOn(); } } }
- 25. 3. Law of Demeter (with) <?php class PC { public function powerOn() { $this->_mobo->powerOn(); } }
- 26. 4. Singleton vs. Factory ● Singleton is static, impossible to mock ● Global state ● Hidden dependency
- 27. 4. Singleton vs. Factory <?php class Authenticator { public function login($user, $pass) { Db::select(...); } }
- 28. 4. Singleton vs. Factory <?php class Authenticator { public function __construct(Db $db) { ... } public function login($user, $pass) { $this->_db->select(...); } }
- 29. Be honest ● If you need something, inject it (or inject its factory) ● Tell > Ask > Look Recipe for a clear, clean Api
- 31. References ● Guide: Writing Testable Code (Misko Hevery) ● Growing Object-Oriented Software, Guided by Tests – Freeman, Price
- 33. Questions? Q/A