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How to (finally) start doing DDD by using BDD
- Howto(finally)startdoing DDDbyusingBDD
- KacperGunia@cakper So!ware Engineer @SensioLabsUK / @Inviqa PHPers Silesia @PHPersPL
- WhatisBDD?
- Bug-driven Development;)
- Behaviour-driven development is about implementing an application by describing its behaviour from the perspective of its stakeholders. -- Dan North
- BDD is about establishing a shared understanding of “done” working from the outside in until you get there -- Dan North
- BDDshowsyouwhattodonext akaTechnicalDiscipline
- HowdoweBDD?
- Feature: Traveler searches for cheap itineraries In order to save money while travelling As a world traveler I want to search for the cheapest itinerary
- Productownerwritesscenario anddeveloperautomatesit
- Developerwritesscenario andthenautomatesit
- No!
- BDDisaboutcommunication! flickr.com/photos/dvids/5638829762
- Scenario: Successfully find cheapest direct flight Given the flight from "WAW" to "LHR" priced $30 was scheduled And the flight from "WAW" to "LHR" priced $50 was scheduled When I open the "/search" page And I fill "WAW" in the "Departure airport" field And I fill "LHR" in the "Destination airport" field And I click "Search" Then I should be redirected to "/results" page And I should see $30 in the "#cheapest-flight-price" block
- Scenario: Successfully find cheapest direct flight Given the flight from "WAW" to "LHR" priced $30 was scheduled And the flight from "WAW" to "LHR" priced $50 was scheduled When I open the "/search" page And I fill "WAW" in the "Departure airport" field And I fill "LHR" in the "Destination airport" field And I click "Search" Then I should be redirected to "/results" page And I should see $30 in the "#cheapest-flight-price" block
- Translation
- Canwedobetter?
- MissionaccomplishedBoys Wecangohomenow! flickr.com/photos/dvids/5638829762
- Translationagain
- Howtofixthat?
- DDD
- WhatisDDDabout?
- It’s about focusing on the domain and letting it affect the so"ware very much -- Jimmy Nilsson
- ButWHYdoweneedit?
- Everybodyknowsthejargon intheirOWNFIELD
- It'saboutcommon understanding
- Ubiquitouslanguage
- Concrete examples are rooted in the problem domain -- Matt Wynne
- DomainModel
- A domain model (...) is not just the knowledge in a domain expert’s head; it is a rigorously organized and selective abstraction of that knowledge -- Eric Evans
- Modeldocuments theknowledge
- Pushing for ubiquitous language hard enough makes your examples a domain model -- Konstantin Kudryashov
- Scenario: Successfully find cheapest direct flight Given the flight from "WAW" to "LHR" priced $30 was scheduled And the flight from "WAW" to "LHR" priced $50 was scheduled When I open the "/search" page And I fill "WAW" in the "Departure airport" field And I fill "LHR" in the "Destination airport" field And I click "Search" Then I should be redirected to "/results" page And I should see $30 in the "#cheapest-flight-price" block
- Scenario: Successfully find cheapest direct itinerary Given the search for the itinerary schedule And the itinerary from "WAW" to "LHR" priced $30 was planned in the schedule And the itinerary from "WAW" to "LHR" priced $50 was planned in the schedule When I search for cheapest itinerary from "WAW" to "LHR" Then the cheapest itinerary should cost $30
- Modellingbyexample
- Phase1
- Scenario: Successfully find cheapest direct itinerary Given the search for the itinerary schedule And the itinerary from "WAW" to "LHR" priced $30 was planned in the schedule And the itinerary from "WAW" to "LHR" priced $50 was planned in the schedule When I search for cheapest itinerary from "WAW" to "LHR" Then the cheapest itinerary should cost $30
- Given the search for the itinerary schedule /** * @Given /^the search for the itinerary schedule$/ */ public function theSearchForTheItinerarySchedule() { $this->itinerarySchedule = new ItinerarySchedule(); $this->search = new Search($this->itinerarySchedule); }
- Designemerges
- And the itinerary from "WAW" to "LHR" priced $30 was planned in the schedule /** * @Given the itinerary from :fromAirport to :toAirport * priced $:price was planned in the schedule */ public function theItineraryFromToPricedWasPlannedInTheSchedule( $fromAirport, $toAirport, $price ) { $itinerary = new Itinerary( Airport::code($fromAirport), Airport::code($toAirport), Money::usd($price) ); $this->itinerarySchedule->plan($itinerary); }
- When I search for cheapest itinerary from "WAW" to "LHR" /** * @When I search for cheapest itinerary from :fromAirport to :toAirport */ public function iSearchForCheapestItineraryFromTo($fromAirport, $toAirport) { $this->cheapestItinerary = $this->search->forCheapest( Airport::code($fromAirport), Airport::code($toAirport) ); }
- Then the cheapest itinerary should cost $30 /** * @Then the cheapest itinerary should cost $:price */ public function theCheapestItineraryShouldCost($price) { expect($this->cheapestItinerary->cost())->toBeLike(Money::usd($price)); }
- Phase2
- @ui Scenario: Successfully find cheapest direct itinerary Given the search for the itinerary schedule And the itinerary from "WAW" to "LHR" priced $30 was planned in the schedule And the itinerary from "WAW" to "LHR" priced $50 was planned in the schedule When I search for cheapest itinerary from "WAW" to "LHR" Then the cheapest itinerary should cost $30
- Given the search for the itinerary schedule /** * @Given the search for the itinerary schedule */ public function theSearchForTheItinerarySchedule() { $this->visit("/search"); }
- And the itinerary from "WAW" to "LHR" priced $30 was planned in the schedule /** * @Given the itinerary from :fromAirport to :toAirport * priced $:price was planned in the schedule */ public function theItineraryFromToPricedWasPlannedInTheSchedule( $fromAirport, $toAirport, $price ) { $itinerary = new Itinerary( Airport::code($fromAirport), Airport::code($toAirport), Money::usd($price) ); $this->get("itinerary_schedule")->plan($itinerary); }
- When I search for cheapest itinerary from "WAW" to "LHR" /** * @When I search for cheapest itinerary from :fromAirport to :toAirport */ public function iSearchForCheapestItineraryFromTo($fromAirport, $toAirport) { $this->fillIn("#from-airport", $fromAirport); $this->fillIn("#to-airport", $toAirport); $this->clickButton("Search"); }
- Then the cheapest itinerary should cost $30 /** * @Then the cheapest itinerary should cost $:price */ public function theCheapestItineraryShouldCost($price) { $cheapestItinerary = $this->find("#cheapest-itinerary"); expect($cheapestItinerary)->toContainText(sprintf("From $%s", $price)); }
- # behat.yml default: suites: domain: contexts: [ SearchContext ] ui: contexts: [ WebSearchContext ] filters: { tags: '@ui' }
- ModellingbyExample Inthree(easy)steps
- · Have the conversation · Model your objects · Go again through UI*
- *But
- You(really)don't havetoautomate everything!
- Butthereisa problem
- Weignoredthedepth ofthedomain
- Onpurpose
- Youcan'tmodelthe wholesystemusing onefeature
- Repeattheprocess andmodelthe planner
- Whatifmodelhasdifferentrequirements inthiscontext?
- BoundedContext
- Languageislimited
- Search Itinerary != Planner Itinerary != Booking Itinerary
- Donotbuildfragilemonoliths!
- Buildapplicationswith Boundedcontextinmind
- ---Wrapup---
- Havethe conversation
- Donotseparatethe conceptsfromthe implementation
- Youcannotbuild conceptualmodels withoutconsidering implementationissues
- Pushfor Ubiquitouslanguage
- UseBehattodriveyourModel NotonlytheUI
- "BDDisabout conversationsyouhaveto producesoftware"
- "DDDisabouthowyou exploredomainmodels andhowyouarticulatethis"
- Thanks! @cakper
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