PHP Barcelona 2010 - Architecture and testability
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This document discusses techniques for improving code testability and maintainability. It recommends: 1. Applying SOLID principles like the single responsibility principle and dependency injection to reduce coupling and improve cohesion. 2. Avoiding direct static method calls and singleton patterns in favor of dependency injection as it allows dependencies to be mocked/stubbed for testing. 3. Following the law of Demeter to avoid excessive coupling between classes. 4. Using factories instead of singletons to allow injecting fakes/mocks for testing. Testing first and listening to tests results in more maintainable code.
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PHP Barcelona 2010 - Architecture and testability
- 1. Architecture and testability Listen to your tests on steroids Giorgio Sironi
- 2. Who I am PHP freelancer from 2005, software architect @ Allbus
- 3. Writer for DZone[, php|architect]
- 4. Bachelor of Computer Engineering @ PoliMi cum laude
- 5. This talk Maintainability, and why testing
- 6. Various techniques to favor ease of testing AND maintainability
- 7. What is maintainability? Being ready to change!
- 8. …but not too much
- 9. Taking the first bullet
- 10. Favored by maintainability New requirements
- 14. Kinds of tests Unit tests (1 object)
- 15. Functional tests (N objects), end-to-end tests (All objects)
- 16. Integration tests (external resources)
- 17. Maintainability (1 of 2) SOLID principles (not all of them) Single responsibility
- 18. Open/closed
- 20. Maintainability (2 of 2) Loose coupling High cohesion Information hiding ...needed from day 1, like readability and testability
- 21. That was the boring part...
- 22. Good but... Good buzzwords, but how do I apply that in practice?
- 23. Testing first Testing first -> Testable code
- 24. Testable code -> Maintainable code
- 25. Maintainable code -> Happy programmer
- 26. Problems with tests A test is slow?
- 27. A test is brittle?
- 28. A test is difficult to write?
- 29. Solution to problems with tests Change the design to ease testing ( listen to your tests )
- 30. Examples of listening to the tests Small tests => high cohesion
- 31. Unit tests => loose coupling
- 32. Fast tests => in-memory isolation
- 33. 4 pillars...
- 34. 1. Dependency injection No new operators outside of Factories
- 35. Easy to change lifecycles and implementations
- 36. 1. Dependency Injection (without) <?php class Ferrari { private $engine ; public function __construct () { $this ->engine = new Engine (); } }
- 37. 1. Dependency Injection (with) <?php class Ferrari { private $engine ; public function __construct (Engine $engine ) { $this ->engine = $engine ; } }
- 38. 2. Avoid static methods Explicit concepts as objects
- 40. 2. Avoid static methods (before) <?php class Collection { public function find ( $key ) { Sorter:: sort ( $this ); // ..search stuff } }
- 41. 2. Avoid using static methods (after) <?php class Collection { public function find ( $key ) { $this ->sorter-> sort ( $this ); // ..search stuff } }
- 42. 3. Law of Demeter Do not walk the... arrows
- 43. Or: don't talk to strangers
- 44. 3. Law of Demeter (without) <?php class PC { public function powerOn () { $this ->mobo->cpu->cache -> powerOn (); } }
- 45. 3. Law of Demeter (with) <?php class PC { public function powerOn () { foreach ( $this ->powered as $item ) { /** @var Powered $item */ $item -> powerOn (); } } }
- 46. 3. Law of Demeter (with) <?php class PC { public function powerOn () { $this ->mobo-> powerOn (); } }
- 47. 4. Singleton vs. Factory A Singleton is hard to mock
- 49. Global state
- 50. 4. Singleton vs. Factory <?php class Authenticator { public function login ( $user , $pass ) { Db:: select (...); } }
- 51. 4. Singleton vs. Factory <?php class Authenticator { public function __construct (Db $db ) { ... } public function login ( $user , $pass ) { $this ->db-> select (...); } }
- 52. Be honest If you need something, inject it (or inject its factory)
- 53. Telling is better than looking around
- 54. Tests are a recipe for clean code
- 55. TDD is... Test-Driven Development Design
- 56. References Guide: Writing Testable Code (Misko Hevery)
- 57. Growing Object-Oriented Software, Guided by Tests – Freeman, Price #goos
- 58. Contacts Personal blog: http://giorgiosironi.blogspot.com
- 60. Questions? Q/A