testing the unpredictable

Non deterministic tests

Transcript

1. TDD 101 4. Testing the unpredictable
2. Testing the unpredictable
3. Testing the unpredictable Elements beyond our system: • Randomness • Time • File system You can’t rely on their behavior
4. How can we test?
5. 1. Things that are using unpredictable components They are global state dependencies Isolate and extract Invert dependency Stub for testing
6. Example class User { private $id; private $name; public function __construct(string $name) { $this->id = Uuid::uuid4(); $this->name = $name; } }
7. Example class User { private $id; private $name; public function __construct( UserId $id, string $name ) { $this->id = $id; $this->name = $name; } }
8. 2. Things that are unpredictable Don’t test what you don’t own Test for properties of the output, not the output itself
9. Example class PasswordGeneratorTest extends TestCase { public function testShouldBeLongEnough() { $password = $this->generator->generate(); $this->assertTrue(strlen($password) > 9); } }
10. Avoid coupling with dependency inversion
11. Dependency Inversion High level modules should not depend on low level modules, both should depend on abstractions. Abstractions should not depend on details. Details should depend on abstractions.
12. Thigh coupling MyClass Dependency Uses
13. Dependency inversion MyClass Interface Dependency Uses Implements
14. Dependency inversion & adapter pattern MyClass Interface Dependency Uses Implements Adapter Uses