Low cost techniques for test doubles

Transcript

1. TDD 101 5. Low cost techniques for doubles
2. Low cost techniques for doubles
3. The point of going low-cost Test should be • Light • Fast • Easy to read • Easy to maintain
4. The point of going low-cost Reduce dependency on mocking frameworks Strictly speaking, mocking frameworks break isolation principle Use the things you have at hand
5. Low cost techniques
6. Techniques at a glance Don’t double (if you don’t really need it) Self shunt Anonymous class
7. Don’t double Use real objects when: • They have no behavior or it is very simple • They have no side effects • They are immutable • They have no dependencies (or depend on similar objects)
8. Don’t double $request = new GetObjectsRequest (‘param1’, ‘param2’); $serviceUnderTest = new Service(); $result = $serviceUnderTest->execute($request); $this->assertEquals(‘expected’, $result);
9. Self-shunt Use the TestCase as double (WTF!) Great for simple doubles Great for early stages of TDD
10. Self-shunt You will need an interface to double Make the test double implement interface You can implement spies
11. Self-shunt stub Class ServiceTest extends TestCase implements GetObjectsRequestInterface { public function testSomething() { $serviceUnderTest = new Service(); $result = $serviceUnderTest->execute($this); $this->assertEquals(‘expected’, $result); } public function param1() { return ‘param1’; } public function param2() { return ‘param2’; } }
12. Self-shunt spy interface CollaboratorInterface { public function doThatThing(): string; } We will need a collaborator for our service
13. Self-shunt spy class ServiceTest extends TestCase 
 implements CollaboratorInterface { private $collaboratorCalls = 0; public function testSomething() { $serviceUnderTest = new Service($this); $result = $serviceUnderTest->execute(); $this->assertEquals(‘expected’, $result); $this->assertEquals(1, $this->collaboratorCalls); } public function doThatThing(): string { $this->collaboratorCalls+; return ‘something’; } }
14. Anonymous class Create doubles on the fly Code exactly what you need Test Abstract classes Doesn’t require a framework
15. Anonymous class Implement interface or subclass May use builders
16. Anonymous class class ServiceTest extends TestCase { public function testSomething() { $collaborator = new class ()
 implements CollaboratorInterface { private $calls = 0; public function doThatThing(): string { $this->calls++; return ‘something’; } public function calls() { return $this->calls; } }; $serviceUnderTest = new Service($collaborator); $result = $serviceUnderTest->execute(); $this->assertEquals(‘expected’, $result); $this->assertEquals(1, $collaborator->calls()); } }