Class inheritance

This view shows what extends what. Select the diagram to zoom in.

The diagram holds 7 inheritance trees, 1 per panel:

• Contexts. WebRawContext extends Mink's RawMinkContext and implements BackendAwareInterface, which the context initializer injects the extension's services through. DrupalContext adds UserAwareInterface, for the user registry and the authenticator. Your project's context extends 1 of the 3.
• Backends. A backend declares each capability it provides as an interface it implements, most of them through its own backend interface, so checking whether it provides a capability is an instanceof. DrupalBackend hands the Drupal work to Core, which the drupal.core option replaces.
• Field handlers. 1 handler per field type, all built on AbstractHandler. The drupal.field_handlers option adds a handler or replaces a shipped one.
• Creation aliases. A creation alias handles a column an entity can't take as written: AuthorAlias turns an author's name into a uid before a node is created, and RolesAlias assigns a user's roles after the user is created.
• Browser adapters. 1 adapter per browser driver family, declaring the browser capabilities that driver provides. A step requests a capability such as JavascriptCapabilityInterface, never a browser driver.
• Entity creation hooks. Each hook attribute, such as #[BeforeEntityCreate], names a call class built on EntityHook, and the hook's scope carries the stub of the entity being created.
• Exceptions. What a failing step throws is part of the public contract, and Exception types says which one when.

The services the extension builds each have 1 implementation of their interface, and Extending the extension layer shows how to put a class of your own in place of one:

Interface	Implementation
Extension\Registry\BackendRegistryInterface	BackendRegistry
Extension\Registry\ScenarioTagRegistryInterface	ScenarioTagRegistry
Extension\Registry\UserRegistryInterface	UserRegistry
Extension\Auth\AuthenticatorInterface, FastLogoutInterface	Authenticator
Extension\Auth\BasicAuthenticatorInterface	BasicAuthenticator
Extension\Http\HttpClientFactoryInterface	HttpClientFactory
Extension\Config\TraitOptionResolverFactoryInterface	TraitOptionResolverFactory
Extension\Config\TraitOptionResolverInterface	TraitOptionResolver
Extension\ServiceContainer\BackendProviderInterface	Extension\Drupal\ServiceContainer\DrupalBackendProvider
Backend\Entity\EntityStubInterface	EntityStub
Backend\Random\RandomGeneratorInterface	RandomGenerator
Backend\Drupal\Core\Field\FieldClassifierInterface	FieldClassifier
Backend\Drupal\Core\Field\FieldShapeClassifierInterface	FieldShapeClassifier
Backend\Drupal\Core\Field\Parser\EntityFieldParserInterface	EntityFieldParser

These classes are where the library plugs into Behat, Mink and Symfony:

Class	Extends or implements
Extension\ServiceContainer\BehatStepsExtension	Behat\Testwork\ServiceContainer\Extension
Extension\ServiceContainer\BackendPass	Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface
Extension\ServiceContainer\Driver\BrowserKitFactory	Behat\MinkExtension\ServiceContainer\Driver\BrowserKitFactory, which it replaces for browserkit_http sessions
Extension\Context\Initializer\BackendAwareInitializer	Behat\Behat\Context\Initializer\ContextInitializer
Extension\Context\Attribute\HookAttributeReader	Behat\Behat\Context\Attribute\AttributeReader
Extension\Listener\BackendListener, SkipTagListener	Symfony\Component\EventDispatcher\EventSubscriberInterface
Extension\Selector\RegionSelector	Behat\Mink\Selector\SelectorInterface
Extension\Generator\ClassGenerator	Behat\Behat\Context\ContextClass\ClassGenerator
Extension\Browser\Element\DocumentElement	Behat\Mink\Element\TraversableElement, aliased over Mink's DocumentElement so page text reads as a browser renders it