behat best practices with symfony

Behat Best Practices with SymfonyCiaran McNulty

@ciaranmcnulty | #symfony_live

Behaviour Driven Development


BDD is the art of using examples in conversations to illustrate behaviour

— Liz Keogh


BDD is the art of using examples in

conversations to illustrate behaviour


Example2 - Something that serves to illustrate or explain a rule— Wiktionary


Rule:We charge our customers sales tax at a rate of 20%



Example:So, if an item is priced at $10, we charge $10 + $2 tax for a total of $12



Example:No! If an item is priced at £10, we charge £10and allocate £1.67 of that as sales tax


Capturing ExamplesInput -> Rules -> Output


Capturing ExamplesInput: When an action is takenOutput: Then an outcome should occur


Capturing ExamplesWhen I buy a pair of Levi 501sThen I am charged £32.99


Capturing ExamplesContext: Given some situationInput: When an action is takenOutput: Then an outcome should occur


Capturing ExamplesGiven Levi 501s are listed at £32.99When I buy a pair of Levi 501sThen I am charged £32.99


Context Questioning“Is there any other context which, when this event happens, will produce a different outcome?” - Liz Keogh


Context QuestioningGiven Levi 501s are listed at £32.99When I buy a pair of Levi 501sThen I am charged £32.99

“Is there any situation where I could buy these jeans and pay a different amount?”


Context QuestioningGiven Levi 501s are listed at £32.99When I buy a pair of Levi 501sThen I am charged £32.99

“Is there any situation where I could buy these jeans and pay a different amount?”

» When they are on sale

» When I get a staff discount

» When they are ex-display@ciaranmcnulty | #symfony_live

Outcome Questioning“Given this context, when this event happens, is there another outcome that’s important? Something we missed, perhaps?” - Liz Keogh


Outcome QuestioningGiven Levi 501s are listed at £32.99When I buy a pair of Levi 501sThen I am charged £32.99

"Aside from me being charged for the jeans, does something else happen that we need to care about?"


Outcome QuestioningGiven Levi 501s are listed at £32.99When I buy a pair of Levi 501sThen I am charged £32.99

"Aside from me being charged for the jeans, does something else happen that we need to care about?"

» I get given a pair of jeans!

» Stock control has to be told we sold them


Validating examples


Behat


Feature: Scheduling a training course

As a trainer In order to be able to cancel courses or schedule new ones I should be able to specify a maximum and minimum class size

Rules: - Course is proposed with size limits - When enough enrolments happen, course is considered viable - When maximum class size is reached, further enrolments are not allowed

Background: Given "BDD for Beginners" was proposed with a class size of 2 to 3 people

Scenario: Course does not get enough enrolments to be viable When only Alice enrols on this course Then this course will not be viable

Scenario: Course gets enough enrolments to be viable Given Alice has already enrolled on this course When Bob enrols on this course Then this course will be viable

Scenario: Enrolments are stopped when class size is reached Given Alice, Bob and Charlie have already enrolled on this course When Derek tries to enrol on this course Then he should not be able to enrol


Feature: Scheduling a training course

As a trainer In order to be able to cancel courses or schedule new ones I should be able to specify a maximum and minimum class size

Rules: - Course is proposed with size limits - When enough enrolments happen, course is considered viable - When maximum class size is reached, further enrolments are not allowed



Scenario: Course does not get enough enrolments to be viable When only Alice enrols on this course Then this course will not be viable



Scenario: Course gets enough enrolments to be viable Given Alice has already enrolled on this course When Bob enrols on this course Then this course will be viable



Scenario: Enrolments are stopped when class size is reached Given Alice, Bob and Charlie have already enrolled on this course When Derek tries to enrol on this course Then he should not be able to enrol


Gherkin:

Given a thing happens to Ciaran

PHP:

/** * @Given a thing happens to :person */public function doAThing(string $person){ // you have to write this}


Driving the Domain layer» Drive PHP objects directly from scenario

» Proves domain supports business actions

» Aligns domain model with business language

» Executes quickly with few dependencies


Given "BDD for Beginners" was proposed with a class size of 2 to 3 peopleWhen only Alice enrols on this courseThen this course will not be viable

class FeatureContext implements Context{ /** * @Given :courseTitle was proposed with a class size of :min to :max people */ public function courseWasProposedWithAClassSizeOfToPeople(string $courseTitle, int $min, int $max) { $this->course = Course::propose( $courseTitle, ClassSize::between($min, $max) ); }}



class FeatureContext implements Context{ /** @Transform */ public function transformLearner(string $name) : Learner { return Learner::called($name); }

/** * @When only :learner enrols on this course */ public function learnerEnrolsOnCourse(Learner $learner) { $this->course->enrol($learner); }}



class FeatureContext implements Context{ /** * @Then this course will not be viable */ public function thisCourseWillNotBeViable() { assert($this->course->isViable() == false); }}


Given "BDD for Beginners" was proposed with a class size of 2 to 3 peopleGiven Alice has already enrolled on this courseWhen Bob enrols on this courseThen this course will be viable

class FeatureContext implements Context{ /** * @When only :learner enrols on this course * @Given :learner has already enrolled on this course */ public function learnerEnrolsOnCourse(Learner $learner) { $this->course->enrol($learner); }}



class FeatureContext implements Context{ /** * @When (only) :learner enrols on this course * @Given :learner has already enrolled on this course */ public function learnerEnrolsOnCourse(Learner $learner) { $this->course->enrol($learner); }}



class FeatureContext implements Context{ /** * @Then this course will be viable */ public function thisCourseWillBeViable() { assert($this->course->isViable() == true); }}


class Course{ //... public function isViable(): bool { return $this->classSize->isViable($this->learners); }}

class ClassSize{ //... public function isViable(int $size) : bool { return $size >= $this->min; }}


class Course{ //... public function isViable() { return $this->classSize->isViable($this->learners); }}

class ClassSize{ //... public function isViable(int $size) { return $size >= $this->min; }}


Given Alice, Bob and Charlie have already enrolled on this courseWhen Derek tries to enrol on this courseThen he should not be able to enrol

class FeatureContext implements Context{ /** * @Given :learner1, :learner2 and :learner3 have already enrolled on this course */ public function learnersHaveAlreadyEnrolledOnThisCourse( Learner $learner1, Learner $learner2, Learner $learner3 ) { $this->course->enrol($learner1); $this->course->enrol($learner2); $this->course->enrol($learner3); }}



class FeatureContext implements Context{ /** * @When :learner tries to enrol on this course */ public function learnerTriesToEnrolOnCourse(Learner $learner) { try { $this->course->enrol($learner); } catch (\Exception $e) { $this->enrolmentProblem = $e; } }}



class FeatureContext implements Context{ /** * @Then (s)he should not be able to enrol */ public function learnerShouldNotBeAbleToEnrol() { assert($this->enrolmentProblem instanceof Cjm\Training\EnrolmentProblem); }}


final class Course{ public function enrol(Learner $learner) { if (!$this->classSize->hasMoreCapacity($this->learners)) { throw new EnrolmentProblem('Class is already at capacity'); }

$this->learners++; }}


Driving the Service layer» Configure services in test SF environment

» Inject services into Behat with behat/symfony2extension

» Interact with domain model via the services

» Aligns service layer with business use cases


# behat.ymldefault: suites: domain: contexts: [ DomainContext ]

services: contexts: [ ServiceContext ]

extensions: Behat\Symfony2Extension: ~



class ServiceContext implements Context{ public function __construct(CourseEnrolments $courseEnrolments) { $this->courseEnrolments = $courseEnrolments; }

/** * @Given :course was proposed with a class size of :min to :max people */ public function wasProposedWithAClassSizeOfToPeople(string $course, int $min, int $max) { $this->course = $course; $this->courseEnrolments->propose($course, $min, $max); }}


# behat.ymldefault: suites: domain: contexts: - DomainContext

services: contexts: - ServiceContext: courseEnrolments: "@cjm.training.enrolment.course_enrolments"

extensions: Behat\Symfony2Extension: ~


class CourseEnrolments{ public function propose(string $title, int $minimum, int $maximum) { $this->courses->add( Course::propose( $title, ClassSize::between($minimum, $maximum) ) ); }}


Repositories» Using real infrastructure is slow

» Using fake infrastructure can lower confidence

» Use fake infrastructure but sync via contract tests


final class Courses implements \Cjm\Training\Enrolment\Model\Courses{ public function add(Course $course) : void { $this->courses[] = $course; }

public function findByTitle(string $title): Course { return $this->courses[0]; }}



class ServiceContext implements Context{ /** * @When (only) :learner enrols on this course */ public function learnerEnrolsOnThisCourse(string $learner) { $this->courseEnrolments->enrol($learner, $this->course); }}



class ServiceContext implements Context{ /** * @Then this course will not be viable */ public function thisCourseWillNotBeViable() { assert($this->courseEnrolments->isCourseViable($this->course) == false); }}


Domain vs Service layer» Start by driving domain layer

» Refactor to services when confidence grows

» Drop back to domain layer when remodelling


Driving the UI layer» Simulate a browser with behat/minkextension

» Interact with domain model via the UI

» Ensures UI supports business actions

» Slow, brittle, flakey...

» Does not constrain API


Don't do thisScenario: Buying a pair of jeans Given I am on "/products/levi-501" When I click on "#add-form input[type=submit]" Then "#basket ul" should contain "jeans"


Mink» Browser driver abstraction

» Supports Selenium, Goutte, Browserkit


# behat.ymlendtoend: filters: tags: "@endtoend" suites: domain: false services: false endtoend: contexts: - EndToEndContext: courseEnrolments: "@cjm.training.enrolment.course_enrolments"


# behat.yml extensions: Behat\Symfony2Extension: env: test_e2e Behat\MinkExtension: sessions: symfony: symfony2: ~



class EndToEndContext implements RawMinkContext{ /** * @Given :course was proposed with a class size of :min to :max people */ public function wasProposedWithAClassSizeOfToPeople(string $course, int $min, int $max) { $this->course = $course; $this->courseEnrolments->propose($course, $min, $max); }}



class EndToEndContext implements RawMinkContext{ /** * @When only :learner enrols on this course */ public function learnerEnrolsOnCourse(string $learner) { $this->visitPath('/courses/' . $this->course);

$page = $this->getSession()->getPage(); $page->fillField('Your name', $learner); $page->pressButton('Enrol'); }}



class EndToEndContext implements RawMinkContext{ /** * @Then this course will not be viable */ public function thisCourseWillNotBeViable() { $this->visitPath('/courses/'.$this->course);

$this->assertSession()->elementExists('css', '#not-viable-warning'); }}


Automating a real browser» Avoid or minimise

» Orders of magnitude slower

» Required for end-to-end with JS

» Replace with JS cucumber stack


# behat.yml extensions: Behat\MinkExtension: sessions: symfony: symfony2: ~ selenium2: browser: chrome capabilities: chrome: switches: - "--headless" - "--disable-gpu"


Summary» Drive domain objects directly to explore model

» Refactor to services when model is stable

» Add minimal UI coverage


Thanks» @ciaranmcnulty

» @Inviqa

» @PhpSpec

» @BDDLondon

github.com/ciaranmcnulty/behat-symfony-demo


behat best practices with symfony

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