Mocking

by @_md

Demystified

how many of youwrite tests?

how manywrite tests before the code?

how many of youknow what a mock is?

how many of you use mocks?

ALL YOU NEED TO KNOW ABOUT TESTING(in 5 minutes)

test

Arrange

Act

Assert

instantiatetested object

test

Arrange

Act

Assert

$parser = new MarkdownParser;

Arrangeinstantiatetested object

test

Arrange

Act

Assert

run the methodyou want to test

$parser = new MarkdownParser;

$html = $parser->toHtml('Hello World');

Actrun the methodyou want to test

test

Arrange

Act

Assert specify theexpected outcome

$parser = new MarkdownParser;$html = $parser->toHtml('Hello World');

assertTrue('<p>Hello World</p>' == $html);

Assertspecify theexpected outcome

test

Arrange

Act

Assert

instantiate tested object

run the method

check expected outcome

$this->toHtml('Hello World') ->shouldReturn('<p>Hello World</p>');

a test is an executable exampleof a class expected behaviour

$this->toHtml('Hello World') ->shouldReturn('<p>Hello World</p>');

READY TO MOCK AROUND?

why?

class ParserSubject{ public function notify(Event $event) { foreach ($this->subscribers as $subscriber) { $subscriber->onChange($event); } }

}

HOW DO I KNOW NOTIFY WORKS?

class ParserSubjectTest extends TestCase{ /** @test */ function it_notifies_subscribers() { // arrange $parser = new ParserSubject; // act // I need an event!!! $parser->notify(/* $event ??? */);

// assert // how do I know subscriber::onChange got called? }

}

HOW DO I KNOW NOTIFY WORKS?

class EndOfListListener extends EventListener{

public function onNewLine(Event $event) { $html = $event->getText(); if ($this->document->getNextLine() == "") { $html .= "</li></ul>"; } return $html; }

}

HOW DO I CONTROL EVENT AND DOCUMENT

focus on unitexpensive to instantiatecontrol on collaborators’ stateindirect outputsundesirable side effects{why?

[Meszaros 2007]

a mock is just 1 ofmany test double patterns

doubles are replacement of anything that is not the tested object

dummyfakestubmockspy{doubles

[Meszaros 2007]

dummyfakestubmockspy{doubles

[Meszaros 2007]

no behaviour

control indirect output

check indirect output

a mockist TDD, London school, approach:

only the tested object is real

DOUBLES WITHOUT BEHAVIOUR

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dummy

test

Arrange

Act

Assert

instantiate (may require collaborators){arrange

class MarkdownParser{ private $eventDispatcher;

public function __construct(EventDispatcher $dispatcher) { $this->eventDispatcher = $dispatcher; }}

USE DOUBLES TO BYPASS TYPE HINTING

class MarkdownParser{ private $eventDispatcher;

public function __construct(EventDispatcher $dispatcher) { $this->eventDispatcher = $dispatcher; }}

USE DOUBLES TO BYPASS TYPE HINTING

class MarkdownParserTest extends TestCase{

function setUp() { $dispatcher = $this->getMock('EventDispatcher'); $this->parser = new MardownParser($dispatcher); }

}

XUNIT EXAMPLE

class MarkdownParser extends ObjectBehavior{

function let($dispatcher) { $dispatcher->beAMockOf('EventDispatcher'); $this->beConstructedWith($dispatcher); }

}

PHPSPEC EXAMPLE

“Dummy is a placeholder passed to the SUT (tested object), but never used”

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[Meszaros 2007]

dummy: double with no behaviour

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DOUBLES TO CONTROL INDIRECT OUPUT

instantiate (may require collaborators)further change state{arrange

class MarkdownParserTest extends TestCase{

function setUp() { $dispatcher = $this->getMock('EventDispatcher'); $this->parser = new MardownParser($dispatcher);

$this->parser->setEncoding('UTF-8');

}

}

FURTHER CHANGE TO THE STATE IN ARRANGE

class MarkdownParserTest extends TestCase{

function setUp() { $dispatcher = $this->getMock('EventDispatcher'); $this->parser = new MardownParser($dispatcher);

$this->parser->setEncoding('UTF-8');

}

}

FURTHER CHANGE TO THE STATE IN ARRANGE

instantiate (may require collaborators)further change stateconfigure indirect output{arrange

class EndOfListListener extends EventListener{

public function onNewLine(Event $event) { $html = $event->getText(); if ($this->document->getNextLine() == "") { $html .= "</li></ul>"; } return $html; }

}

INDIRECT OUTPUTS

class EndOfListListener extends EventListener{

public function onNewLine(Event $event) { $html = $event->getText(); if ($this->document->getNextLine() == "") { $html .= "</li></ul>"; } return $html; }

}

INDIRECT OUTPUTS

doubles for controlling indirect output

fake stub

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$event->getText(); // will return “Hello World”$this->document->getNextLine(); // will return “”

STUBBING: CONTROLLING DOUBLES INDIRECT OUTPUTS

IN PHPSPEC

function let($event, $document){ $event->beAMockOf("Event"); $document->beAMockOf("Document"); $this->beConstructedWith($document);}

IN PHPSPEC

function let($event, $document){ $event->beAMockOf("Event"); $document->beAMockOf("Document"); $this->beConstructedWith($document);}

function it_ends_list_when_next_is_empty($event, $document){ $event->getText()->willReturn("Some text"); $document->getNextLine()->willReturn("");

}

IN PHPSPEC

function let($event, $document){ $event->beAMockOf("Event"); $document->beAMockOf("Document"); $this->beConstructedWith($document);}

function it_ends_list_when_next_is_empty($event, $document){ $event->getText()->willReturn("Some text"); $document->getNextLine()->willReturn("");

$this->onNewLine($event) ->shouldReturn("Some text</li></ul>");

}

class EndOfListListener extends EventListener{

public function onNewLine(Event $event) { $html = $event->getText(); if ($this->document->getNextLine() == "") { $html .= "</li></ul>"; } return $html; }

}

THE CODE AGAIN

THE SPEC AGAIN

function let($event, $document){ $event->beAMockOf("Event"); $document->beAMockOf("Document"); $this->beConstructedWith($document);}

function it_ends_list_when_next_is_empty($event, $document){ $event->getText()->willReturn("Some text"); $document->getNextLine()->willReturn("");

$this->onNewLine($event) ->shouldReturn("Some text</li></ul>");

}

loose demandfakestub

returns null to any method call

double behaviour

returns null to defined set methods

returns value defined or raise error

DOUBLES TO SPEC MESSAGE EXCHANGE

we said before

a test is an executable exampleof a class expected behaviour

what is behaviour?

B = I + O

behaviour = input + output

what can happen in a method?

return a value modify stateprint somethingthrow an exceptiondelegate{methods

return a value modify stateprint somethingthrow an exceptiondelegate{methods

not the final behaviour

return a value print somethingthrow an exceptiondelegate{methods

we should probably delegate that too

return a value throw an exceptiondelegate{methods

returns a value throws an exception

delegates

method strategy

returns a value throws an exception

delegates

assertions/expectations

mocks & spies

method strategy

“The key in making great and growable systems is much more to

design how its modules communicate

rather than what their internal propertiesand behaviours should be.”

Messaging

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messaging

yeah, but what does it mean?

$this->person->getCar()->getEngine()->ignite();

Inappropriate Intimacy

$this->person->startCar();

tell, don’t ask!

[Sharp 1997]

exposing lower level implementationmakes the code rigid

$this->person->getCar()->getEngine()->ignite();

focus on messagingmakes the code flexible

$this->person->startCar();

doubles for messaging

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mock spy

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class ParserSubject{ public function notify(Event $event) { foreach ($this->subscribers as $subscriber) { $subscriber->onChange($event); } }

}

HOW DO I KNOW NOTIFY WORKS?

class ParserSubject{ public function notify(Event $event) { foreach ($this->subscribers as $subscriber) { $subscriber->onChange($event); } }

}

HOW DO I KNOW NOTIFY WORKS?

use mocks to describe how your method will impact collaborators

use PHPUnit_Framework_TestCase as TestCase;

class ParserSubjectTest extends TestCase{ /** @test */ function it_notifies_subscribers() { $event = $this->getMock("Event");

$subscriber = $this->getMock("Subscriber"); $subscriber->expects($this->once()) ->method("onChange") ->with($event);

$parser = new ParserSubject(); $parser->attach($subscriber); $parser->notify($event); }}

USING PHPUNIT NATIVE MOCK CONSTRUCT

public function testUpdateWithEqualTypes(){ $installer = $this->createInstallerMock(); $manager = new InstallationManager('vendor'); $manager->addInstaller($installer);

$initial = $this->createPackageMock(); $target = $this->createPackageMock(); $operation = new UpdateOperation($initial, $target, 'test');

$initial ->expects($this->once()) ->method('getType') ->will($this->returnValue('library')); $target ->expects($this->once()) ->method('getType') ->will($this->returnValue('library'));

$installer ->expects($this->once()) ->method('supports') ->with('library') ->will($this->returnValue(true));

$installer ->expects($this->once()) ->method('update') ->with($this->repository, $initial, $target);

EXCESSIVE SETUP

github.com/padraicb/mockery

use PHPUnit_Framework_TestCase as TestCase;

class ParserSubjectTest extends TestCase{ /** @test */ function it_notifies_subscribers() { $event = Mockery::mock("Event");

$subscriber = Mockery::mock("Subscriber"); $subscriber->shouldReceive("onChange") ->with($event);

$parser = new ParserSubject(); $parser->attach($subscriber); $parser->notify($event); }}

USING MOCKERY

class ParserSubject extends PHPSpec2\ObjectBehavior{ /** * @param Event $event * @param Subscriber $subscriber */ function it_notifies_subscribers($event, $subscriber) { $subscriber->onChange($event)->shouldBeCalled(); $this->attach($subscriber); $this->notify($event); }}

SAME EXAMPLE IN PHPSPEC

use spies to describe indirect output expectations, retrospectively

github.com/dancras/doubles

use PHPSpec2\ObjectBehavior;

class ParserSubject extends ObjectBehavior{ function it_notifies_subscribers() { $event = Doubles::fromClass('\Event'); $subscriber = Doubles::fromClass('\Subscriber'); $this->attach($subscriber); $this->notify($event);

$subscriber->spy('onChange')->callCount()->shoudBe(1);

}}

SPY EXAMPLE – WITH “DOUBLES” FRAMEWORK

use PHPSpec2\ObjectBehavior;

class ParserSubject extends ObjectBehavior{ /** * @param Event $event * @param Subscriber $subscriber */ function it_notifies_subscribers($event, $subscriber) { $this->attach($subscriber); $this->notify($event); $subscriber->onChange($event) ->shouldHaveBeenCalled(); }}

SPY EXAMPLE – AVAILABLE WITH PROPHECY INTEGRATION

use Prophecy\Prophet;

class TestCase extends SomeUnitTestingFrameworkTestCase{ function createDoubler($name) { $this->prophet = new \Prophecy\Prophet; return $this->prophet->prophesize($name); }

function createDummy($name) { return $this->createDoubler($name)->reveal(); }}

INTEGRATING PROPHECY

dummyfakestubmockspy{doubles

[Meszaros 2007]

no behaviour

control indirect output

messaging

I work here

I contribute here

I tweet here @_md

Marcello Duarte

Thank you !

Questions or Comments?

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