Behat Best Practices with Symfony

Behat Best Practices with
Symfony
Ciaran McNulty
Crania Ltd | @ciaranmcnulty | #symfonycon

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

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

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

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

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

Capturing Examples
Action Outcome
What causes the behaviour? What is the result of the
behaviour?

Capturing Examples
Action Outcome
What causes the behaviour? What is the result of the
behaviour?
I buy a pair of Levi 501s I am charged £32.99

Why does that action
cause that outcome?

Capturing Examples
Context Action Outcome
What happened in
the past that affects
the behaviour?
What causes the
behaviour?
What is the result of
the behaviour?
Levi 501s are listed
at £32.99
I buy a pair of Levi
501s
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 Questioning
at £32.99
501s
“Is there any situation where I could buy these jeans and pay a different
amount?”

Context Questioning
Levi 501s are listed at
£32.99
I buy a pair of Levi 501s I am charged £32.99
Levis are on sale " ?
Purchaser is a staff
member
" ?
The jeans are damaged " ?

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

Outcome Questioning
at £32.99
501s
"Aside from me being charged for the jeans, does something else
happen that we need to care about?"

Outcome Questioning
at £32.99
501s
I am charged
£32.99 ...and I get
sent some
jeans ...and the
warehouse stock
level is reduced

Example Mapping
Matt Wynne

Outstanding questions
» Can we start work on this item without this answer?
» Do we need to resolve it first?
» Can the story be split along this seam?

Example mapping
» One-on-one
» Large group
» Round-robin

Feature Mapping
John Ferguson Smart

Event Storming
Alberto Brandolini

BDD is not about
testing

BDD is also not about
one-way requirement
capture

Validating examples
(ok it is a bit about testing,
sometimes)

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

Background:
Scenario: Course does not get enough enrolments to be viable

Background:
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

Background:
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

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)
);
}
}

{
/** @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);
}
}

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

Driving the Service layer
» Configure services in test environment
» Inject services into Behat context (using an extension)
» Interact with domain model via the services
» Aligns service layer with business use cases

Suites
# behat.yml
default:
suites:
domain:
contexts: [ DomainContext ]
services:
contexts: [ ServiceContext ]

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);
}
}

{
public function __construct(CourseEnrolments $courseEnrolments)
{
$this->courseEnrolments = $courseEnrolments;
}
/**
*/
{
$this->courseId = $course;
}
}

Symfony extension
# behat.yml
default:
suites:
domain:
contexts:
- DomainContext
services:
contexts:
- ServiceContext:
courseEnrolments: "@cjm.training.enrolment.course_enrolments"
extensions:
BehatSymfony2Extension: ~

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

Infrastructure
» Using real infrastructure is slow
» Using fake infrastructure can lower confidence
» Use fake infrastructure but sync via contract tests

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

{
/**
*/
{
assert($this->courseEnrolments->isCourseViable($this->courseId) == 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 this
Scenario: 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.yml
deafult:
suites:
services:
contexts:
- ServiceContext:
endtoend:
ﬁlters:
tags: "@endtoend"
contexts:
- EndToEndContext:

Mink with Symfony
# behat.yml
extensions:
BehatMinkExtension:
sessions:
symfony:
symfony2: ~

Mink with PSR-7
# behat.yml
extensions:
CjmBehatPsr7Extension:
app: %paths.base%/path/to/ﬁle.php
BehatMinkExtension:
sessions:
psr:
psr-7: ~

class EndToEndContext implements RawMinkContext
{
/**
*/
{
$this->course = $course;
}
}

{
/**
* @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');
}
}

{
/**
*/
{
$this->visitPath('/courses/'.$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
» Can often be replaced with JS cucumber stack

# behat.yml
extensions:
DMoreChromeExtensionBehatServiceContainerChromeExtension: ~
BehatMinkExtension:
sessions:
symfony:
symfony2: ~
chrome-driver:
chrome:
api_url: "http://localhost:9222"

chrome --disable-gpu --headless
--remote-debugging-address=0.0.0.0
--remote-debugging-port=9222
or
docker run -d -p 9222:9222
--cap-add=SYS_ADMIN
justinribeiro/chrome-headless

Summary
» Drive domain objects directly to explore model
» Refactor to services when model is stable
» Add minimal UI coverage

Future
» Autowiring
» Panther support
» Cucumberification

Thanks
» @ciaranmcnulty
» @PhpSpec
» @BDDLondon
» @SymfonyUK
github.com/ciaranmcnulty/behat-symfony-demo

Behat Best Practices with Symfony

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