Mocking Demystified
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PHPSpec - the only Design Tool you need - 4Developers
- PHPSpec the only Design Tool you need flickr.com/mobilestreetlife/4179063482/
- Kacper Gunia @cakper Software Engineer @SensioLabsUK Symfony Certified Developer PHPers Silesia @PHPersPL
- ! ‘Is my code well designed?’
- ’That’s not the way I would have done it…’
- It’s hard to change!
- We're afraid to change it…
- We cannot reuse it!
- So what Design is about?
- ‘The key in making great and growable systems is much more to design how its modules communicate rather than what their internal properties and behaviors should be.’ Alan Kay
- Design is about Messaging
- $orders = $orderRepository -‐>getEntityManager() -‐>createOrderQuery($customer) -‐>execute();
- $orders = $orderRepository -‐>findBy($customer); !
- We have to refactor! :)
- We need two weeks to refactor! :)
- We need two sprints to refactor! :|
- We need two months to refactor! :/
- Refactoring is the process of restructuring existing code without changing its external behavior
- 4 Rules of Simple Design 1. Passes its tests 2. Minimizes duplication 3. Maximizes clarity 4. Has fewer elements
- …so we need to write Tests!
- how to write Tests?
- Tests Driven Development
- Red GreenRefactor
- Red GreenRefactor
- But!
- How to test something that doesn’t exist? flickr.com/ucumari/580865728/
- Test in TDD means specification
- Specification describes behavior
- Behavior Driven Development
- BDD improves Naming Conventions Tools
- Story BDD vs Spec BDD
- Story BDD description of business-targeted application behavior
- Spec BDD specification for low-level implementation
- http://phpspec.net/
- Spec BDD tool created by @_md & @everzet
- Bundled with mocking library Prophecy
- composer create-‐project cakper/phpspec-‐standard project-‐name
- But!
- Isn’t it a tool just like PHPUnit?
- PHPUnit is a Testing Tool
- PHPSpec is the Design Tool
- class CustomerRepositoryTest extends PHPUnit_Framework_TestCase { function testClassExists() { $customerRepository = new CustomerRepository; ! $customer = $customerRepository-‐>findById(5); $this-‐>assertInstanceOf('Customer', $customer); } }
- class CustomerRepositorySpec extends ObjectBehavior { function it_is_initializable() { $this-‐>shouldHaveType('CustomerRepository'); } }
- Naming
- TestCase ! Specification
- Test ! Example
- Assertion ! Expectation
- OK, so how to specify a method?
- What method can do? return a value modify state delegate throw an exception
- Command-Query Separation
- Command change the state of a system but do not return a value
- Query return a result and do not change the state of the system (free of side effects)
- Never both!
- class CustomerRepositorySpec extends ObjectBehavior { function it_loads_user_preferences() { $customer = $this-‐>findById(5); ! $customer-‐>shouldBeAnInstanceOf('Customer'); } }
- Matchers
- Type shouldBeAnInstanceOf(*) shouldReturnAnInstanceOf(*) shouldHaveType(*)
- $customer-‐>shouldBeAnInstanceOf('Customer');
- Identity === shouldReturn(*) shouldBe(*) shouldEqual(*) shouldBeEqualTo(*)
- $this-‐>findById(-‐1)-‐>shouldReturn(null);
- Comparison == shouldBeLike(*)
- $this-‐>getAmount()-‐>shouldBeLike(5);
- Throw throw(*)->during*()
- $this-‐>shouldThrow(‘InvalidArgumentException’) -‐>duringFindByCustomer(null);
- Object State shouldHave*()
- $car-‐>hasEngine(); ! $this-‐>shouldHaveEngine();
- Scalar shouldBeString() shouldBeArray()
- Count shouldHaveCount(*)
- Or write your own Inline Matcher
- function it_should_have_poland_as_avialable_country() { $this-‐>getCountryCodes()-‐>shouldHaveValue('PL'); } ! public function getMatchers() { return [ 'haveValue' => function ($subject, $value) { return in_array($value, $subject); } ]; }
- But!
- Design is about Messaging!
- And (so far) there is no messaging…
- London School
- Mockist TDD only tested object is real
- Test Doubles
- Dummy tested code requires parameter but doesn’t need to use it
- function let(EntityManager $entityManager) { $this-‐>beConstructedWith($entityManager); } ! function it_returns_customer_by_id() { $customer = $this-‐>findById(5); ! $customer-‐>shouldBeAnInstanceOf('Customer'); } }
- function let(EntityManager $entityManager) { $this-‐>beConstructedWith($entityManager); } ! function it_returns_customer_by_id() { $customer = $this-‐>findById(5); ! $customer-‐>shouldBeAnInstanceOf('Customer'); } }
- Stub provides "indirect input" to the tested code
- function it_bolds_the_output(Stream $stream) { $stream-‐>getOutput() -‐>willReturn('4 Developers'); ! $this-‐>bold($stream) -‐>shouldReturn('<b>4 Developers</b>’); }
- function it_bolds_the_output(Stream $stream) { $stream-‐>getOutput() -‐>willReturn('4 Developers'); ! $this-‐>bold($stream) -‐>shouldReturn('<b>4 Developers</b>’); }
- Mocks verifies "indirect output” of the tested code
- function let(Logger $logger) { $this-‐>beConstructedWith($logger); } ! function it_returns_customer_by_id(Logger $logger) { $logger-‐>debug('DB queried') -‐>shouldBeCalled(); ! $this-‐>findById(5); }
- function let(Logger $logger) { $this-‐>beConstructedWith($logger); } ! function it_returns_customer_by_id(Logger $logger) { $logger-‐>debug('DB queried') -‐>shouldBeCalled(); ! $this-‐>findById(5); }
- Spy verifies "indirect output” by asserting the expectations afterwards
- function let(Logger $logger) { $this-‐>beConstructedWith($logger); } ! function it_returns_customer_by_id(Logger $logger) { $this-‐>findById(5); ! $logger-‐>debug('DB queried') -‐>shouldHaveBeenCalled(); }
- function let(Logger $logger) { $this-‐>beConstructedWith($logger); } ! function it_returns_customer_by_id(Logger $logger) { $this-‐>findById(5); ! $logger-‐>debug('DB queried') -‐>shouldHaveBeenCalled(); }
- (a bit more) complex example
- function let(SecurityContext $securityContext) { $this-‐>beConstructedWith($securityContext); } ! function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function let(SecurityContext $securityContext) { $this-‐>beConstructedWith($securityContext); } ! function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function let(SecurityContext $securityContext) { $this-‐>beConstructedWith($securityContext); } ! function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function let(SecurityContext $securityContext) { $this-‐>beConstructedWith($securityContext); } ! function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function let(SecurityContext $securityContext) { $this-‐>beConstructedWith($securityContext); } ! function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- But mocking becomes painful…
- And it smells…
- Law of Demeter unit should only talk to its friends; don't talk to strangers
- It’s time to refactor! :)
- function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function it_returns_user_from_token( SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $this-‐>getUser()-‐>shouldRetun($user); } !
- public function __construct(SecurityContext $securityContext){ $this-‐>securityContext = $securityContext; } ! public function getUser() { $token = $this-‐>securityContext-‐>getToken(); if ($token instanceof TokenInterface) { return $token-‐>getUser(); } ! return null; }
- function it_loads_user_preferences( GetResponseEvent $event, SecurityContext $securityContext, TokenInterface $token, User $user) { $securityContext-‐>getToken()-‐>willReturn($token); $token-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type('Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function it_loads_user_preferences( GetResponseEvent $event, DomainSecurityContext $securityContext, User $user) { $securityContext-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type(‘Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- Composition over Inheritance separation of concerns small, well focused objects composition is simpler to test
- public function __construct(SecurityContext $securityContext){ $this-‐>securityContext = $securityContext; } ! public function getUser() { $token = $this-‐>securityContext-‐>getToken(); if ($token instanceof TokenInterface) { return $token-‐>getUser(); } ! return null; }
- We can still improve
- function it_loads_user_preferences( GetResponseEvent $event, DomainSecurityContext $securityContext, User $user) { $securityContext-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type(‘Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- function it_loads_user_preferences( GetResponseEvent $event, DomainSecurityContextInterface $securityContext, User $user) { $securityContext-‐>getUser()-‐>willReturn($user); ! $user-‐>setPreferences(Argument::type(‘Preferences')) -‐>shouldBeCalled(); ! $this-‐>handle($event); }
- Dependency Inversion Principle
- high-level modules should not depend on low-level modules; both should depend on abstractions DIP states:
- DIP states: abstractions should not depend upon details; details should depend upon abstractions
- Isn’t it overhead?
- What are benefits of using PHPSpec?
- TDD-cycle oriented tool
- ease Mocking
- focused on Messaging
- encourage injecting right Collaborators
- and following Demeter Low
- enables Refactoring
- and gives you Regression Safety
- and it’s trendy ;)
- Is PHPSpec the only design tool we need?
- s
- So it helps ;)
- Kacper Gunia Software Engineer Symfony Certified Developer PHPers Silesia Thanks!
