// A link relation type of the "extension" kind.
/** @var \Drupal\Core\Http\LinkRelationTypeInterface $canonical */ $add_form = $link_relation_type_manager->createInstance('add-form'); $this->assertInstanceOf(LinkRelationType::class, $add_form); $this->assertFalse($add_form->isRegistered()); $this->assertTrue($add_form->isExtension());