class EntityCacheTagsTestBase

abstract class EntityCacheTagsTestBase extends PageCacheTagsTestBase {
    
    /**
     * Modules to enable.
     *
     * @var array
     */
    protected static $modules = [
        'entity_test',
        'field_test',
    ];
    
    /**
     * The main entity used for testing.
     *
     * @var \Drupal\Core\Entity\EntityInterface
     */
    protected $entity;
    
    /**
     * The entity instance referencing the main entity.
     *
     * @var \Drupal\Core\Entity\EntityInterface
     */
    protected $referencingEntity;
    
    /**
     * The entity instance not referencing the main entity.
     *
     * @var \Drupal\Core\Entity\EntityInterface
     */
    protected $nonReferencingEntity;
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        // Give anonymous users permission to view test entities, so that we can
        // verify the cache tags of cached versions of test entity pages.
        $user_role = Role::load(RoleInterface::ANONYMOUS_ID);
        $user_role->grantPermission('view test entity');
        $user_role->save();
        // Create an entity.
        $this->entity = $this->createEntity();
        // If this is an entity with field UI enabled, then add a configurable
        // field. We will use this configurable field in later tests to ensure that
        // field configuration invalidate render cache entries.
        if ($this->entity
            ->getEntityType()
            ->get('field_ui_base_route')) {
            // Add field, so we can modify the field storage and field entities to
            // verify that changes to those indeed clear cache tags.
            FieldStorageConfig::create([
                'field_name' => 'configurable_field',
                'entity_type' => $this->entity
                    ->getEntityTypeId(),
                'type' => 'test_field',
                'settings' => [],
            ])
                ->save();
            FieldConfig::create([
                'entity_type' => $this->entity
                    ->getEntityTypeId(),
                'bundle' => $this->entity
                    ->bundle(),
                'field_name' => 'configurable_field',
                'label' => 'Configurable field',
                'settings' => [],
            ])
                ->save();
            // Reload the entity now that a new field has been added to it.
            $storage = $this->container
                ->get('entity_type.manager')
                ->getStorage($this->entity
                ->getEntityTypeId());
            $storage->resetCache();
            $this->entity = $storage->load($this->entity
                ->id());
        }
        // Create a referencing and a non-referencing entity.
        [
            $this->referencingEntity,
            $this->nonReferencingEntity,
        ] = $this->createReferenceTestEntities($this->entity);
    }
    
    /**
     * Creates the entity to be tested.
     *
     * @return \Drupal\Core\Entity\EntityInterface
     *   The entity to be tested.
     */
    protected abstract function createEntity();
    
    /**
     * Returns the access cache contexts for the tested entity.
     *
     * Only list cache contexts that aren't part of the required cache contexts.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity to be tested, as created by createEntity().
     *
     * @return string[]
     *   An array of the additional cache contexts.
     *
     * @see \Drupal\Core\Entity\EntityAccessControlHandlerInterface
     */
    protected function getAccessCacheContextsForEntity(EntityInterface $entity) {
        return [];
    }
    
    /**
     * Returns the additional (non-standard) cache contexts for the tested entity.
     *
     * Only list cache contexts that aren't part of the required cache contexts.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity to be tested, as created by createEntity().
     *
     * @return string[]
     *   An array of the additional cache contexts.
     *
     * @see \Drupal\Tests\system\Functional\Entity\EntityCacheTagsTestBase::createEntity()
     */
    protected function getAdditionalCacheContextsForEntity(EntityInterface $entity) {
        return [];
    }
    
    /**
     * Returns the additional (non-standard) cache tags for the tested entity.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity to be tested, as created by createEntity().
     *
     * @return array
     *   An array of the additional cache tags.
     *
     * @see \Drupal\Tests\system\Functional\Entity\EntityCacheTagsTestBase::createEntity()
     */
    protected function getAdditionalCacheTagsForEntity(EntityInterface $entity) {
        return [];
    }
    
    /**
     * Returns the additional cache tags for the tested entity's listing by type.
     *
     * @return string[]
     *   An array of the additional cache contexts.
     */
    protected function getAdditionalCacheContextsForEntityListing() {
        return [];
    }
    
    /**
     * Returns the additional cache tags for the tested entity's listing by type.
     *
     * Necessary when there are unavoidable default entities of this type, e.g.
     * the anonymous and administrator User entities always exist.
     *
     * @return array
     *   An array of the additional cache tags.
     */
    protected function getAdditionalCacheTagsForEntityListing() {
        return [];
    }
    
    /**
     * Selects the preferred view mode for the given entity type.
     *
     * Prefers 'full', picks the first one otherwise, and if none are available,
     * chooses 'default'.
     */
    protected function selectViewMode($entity_type) {
        $view_modes = \Drupal::entityTypeManager()->getStorage('entity_view_mode')
            ->loadByProperties([
            'targetEntityType' => $entity_type,
        ]);
        if (empty($view_modes)) {
            return 'default';
        }
        else {
            // Prefer the "full" display mode.
            if (isset($view_modes[$entity_type . '.full'])) {
                return 'full';
            }
            else {
                $view_modes = array_keys($view_modes);
                return substr($view_modes[0], strlen($entity_type) + 1);
            }
        }
    }
    
    /**
     * Creates a referencing and a non-referencing entity for testing purposes.
     *
     * @param \Drupal\Core\Entity\EntityInterface $referenced_entity
     *   The entity that the referencing entity should reference.
     *
     * @return \Drupal\Core\Entity\EntityInterface[]
     *   An array containing a referencing entity and a non-referencing entity.
     */
    protected function createReferenceTestEntities($referenced_entity) {
        // All referencing entities should be of the type 'entity_test'.
        $entity_type = 'entity_test';
        // Create a "foo" bundle for the given entity type.
        $bundle = 'foo';
        entity_test_create_bundle($bundle, NULL, $entity_type);
        // Add a field of the given type to the given entity type's "foo" bundle.
        $field_name = $referenced_entity->getEntityTypeId() . '_reference';
        FieldStorageConfig::create([
            'field_name' => $field_name,
            'entity_type' => $entity_type,
            'type' => 'entity_reference',
            'cardinality' => FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED,
            'settings' => [
                'target_type' => $referenced_entity->getEntityTypeId(),
            ],
        ])
            ->save();
        FieldConfig::create([
            'field_name' => $field_name,
            'entity_type' => $entity_type,
            'bundle' => $bundle,
            'settings' => [
                'handler' => 'default',
                'handler_settings' => [
                    'target_bundles' => [
                        $referenced_entity->bundle() => $referenced_entity->bundle(),
                    ],
                    'sort' => [
                        'field' => '_none',
                    ],
                    'auto_create' => FALSE,
                ],
            ],
        ])
            ->save();
        
        /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
        $display_repository = \Drupal::service('entity_display.repository');
        if (!$this->entity
            ->getEntityType()
            ->hasHandlerClass('view_builder')) {
            $display_repository->getViewDisplay($entity_type, $bundle, 'full')
                ->setComponent($field_name, [
                'type' => 'entity_reference_label',
            ])
                ->save();
        }
        else {
            $referenced_entity_view_mode = $this->selectViewMode($this->entity
                ->getEntityTypeId());
            $display_repository->getViewDisplay($entity_type, $bundle, 'full')
                ->setComponent($field_name, [
                'type' => 'entity_reference_entity_view',
                'settings' => [
                    'view_mode' => $referenced_entity_view_mode,
                ],
            ])
                ->save();
        }
        // Create an entity that does reference the entity being tested.
        $label_key = \Drupal::entityTypeManager()->getDefinition($entity_type)
            ->getKey('label');
        $referencing_entity = $this->container
            ->get('entity_type.manager')
            ->getStorage($entity_type)
            ->create([
            $label_key => 'Referencing ' . $entity_type,
            'status' => 1,
            'type' => $bundle,
            $field_name => [
                'target_id' => $referenced_entity->id(),
            ],
        ]);
        $referencing_entity->save();
        // Create an entity that does not reference the entity being tested.
        $non_referencing_entity = $this->container
            ->get('entity_type.manager')
            ->getStorage($entity_type)
            ->create([
            $label_key => 'Non-referencing ' . $entity_type,
            'status' => 1,
            'type' => $bundle,
        ]);
        $non_referencing_entity->save();
        return [
            $referencing_entity,
            $non_referencing_entity,
        ];
    }
    
    /**
     * Tests cache tags presence and invalidation of the entity when referenced.
     *
     * Tests the following cache tags:
     * - entity type view cache tag: "<entity type>_view"
     * - entity cache tag: "<entity type>:<entity ID>"
     * - entity type list cache tag: "<entity type>_list"
     * - referencing entity type view cache tag: "<referencing entity type>_view"
     * - referencing entity type cache tag: "<referencing entity type>:<referencing entity ID>"
     */
    public function testReferencedEntity() : void {
        $entity_type = $this->entity
            ->getEntityTypeId();
        $referencing_entity_url = $this->referencingEntity
            ->toUrl('canonical');
        $non_referencing_entity_url = $this->nonReferencingEntity
            ->toUrl('canonical');
        $listing_url = Url::fromRoute('entity.entity_test.collection_referencing_entities', [
            'entity_reference_field_name' => $entity_type . '_reference',
            'referenced_entity_type' => $entity_type,
            'referenced_entity_id' => $this->entity
                ->id(),
        ]);
        $empty_entity_listing_url = Url::fromRoute('entity.entity_test.collection_empty', [
            'entity_type_id' => $entity_type,
        ]);
        $nonempty_entity_listing_url = Url::fromRoute('entity.entity_test.collection_labels_alphabetically', [
            'entity_type_id' => $entity_type,
        ]);
        // The default cache contexts for rendered entities.
        $default_cache_contexts = [
            'languages:' . LanguageInterface::TYPE_INTERFACE,
            'theme',
            'user.permissions',
        ];
        $entity_cache_contexts = Cache::mergeContexts($default_cache_contexts, [
            'url.site',
        ]);
        $page_cache_contexts = Cache::mergeContexts($default_cache_contexts, [
            'url.query_args:' . MainContentViewSubscriber::WRAPPER_FORMAT,
            'user.roles:authenticated',
        ]);
        // Cache tags present on every rendered page.
        // 'user.permissions' is a required cache context, and responses that vary
        // by this cache context when requested by anonymous users automatically
        // also get this cache tag, to ensure correct invalidation.
        $page_cache_tags = Cache::mergeTags([
            'http_response',
            'rendered',
        ], [
            'config:user.role.anonymous',
        ]);
        // If the block module is used, the Block page display variant is used,
        // which adds the block config entity type's list cache tags.
        $page_cache_tags = Cache::mergeTags($page_cache_tags, \Drupal::moduleHandler()->moduleExists('block') ? [
            'config:block_list',
        ] : []);
        $page_cache_tags_referencing_entity = in_array('user.permissions', $this->getAccessCacheContextsForEntity($this->referencingEntity)) ? [
            'config:user.role.anonymous',
        ] : [];
        $view_cache_tag = [];
        if ($this->entity
            ->getEntityType()
            ->hasHandlerClass('view_builder')) {
            $view_cache_tag = \Drupal::entityTypeManager()->getViewBuilder($entity_type)
                ->getCacheTags();
        }
        $context_metadata = \Drupal::service('cache_contexts_manager')->convertTokensToKeys($entity_cache_contexts);
        $cache_context_tags = $context_metadata->getCacheTags();
        // Generate the cache tags for the (non) referencing entities.
        $referencing_entity_cache_tags = Cache::mergeTags($this->referencingEntity
            ->getCacheTags(), \Drupal::entityTypeManager()->getViewBuilder('entity_test')
            ->getCacheTags());
        // Includes the main entity's cache tags, since this entity references it.
        $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, $this->entity
            ->getCacheTags());
        $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
        $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, $view_cache_tag);
        $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, $cache_context_tags);
        $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, [
            'rendered',
        ]);
        $non_referencing_entity_cache_tags = Cache::mergeTags($this->nonReferencingEntity
            ->getCacheTags(), \Drupal::entityTypeManager()->getViewBuilder('entity_test')
            ->getCacheTags());
        $non_referencing_entity_cache_tags = Cache::mergeTags($non_referencing_entity_cache_tags, [
            'rendered',
        ]);
        // Generate the cache tags for all two possible entity listing paths.
        // 1. list cache tag only (listing query has no match)
        // 2. list cache tag plus entity cache tag (listing query has a match)
        $empty_entity_listing_cache_tags = Cache::mergeTags($this->entity
            ->getEntityType()
            ->getListCacheTags(), $page_cache_tags);
        $nonempty_entity_listing_cache_tags = Cache::mergeTags($this->entity
            ->getEntityType()
            ->getListCacheTags(), $this->entity
            ->getCacheTags());
        $nonempty_entity_listing_cache_tags = Cache::mergeTags($nonempty_entity_listing_cache_tags, $this->getAdditionalCacheTagsForEntityListing());
        $nonempty_entity_listing_cache_tags = Cache::mergeTags($nonempty_entity_listing_cache_tags, $page_cache_tags);
        $this->verifyPageCache($referencing_entity_url, 'MISS');
        // Verify a cache hit, but also the presence of the correct cache tags.
        $expected_tags = Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags);
        $expected_tags = Cache::mergeTags($expected_tags, $page_cache_tags_referencing_entity);
        $this->verifyPageCache($referencing_entity_url, 'HIT', $expected_tags);
        // Also verify the existence of an entity render cache entry.
        $cache_keys = [
            'entity_view',
            'entity_test',
            $this->referencingEntity
                ->id(),
            'full',
        ];
        $access_cache_contexts = $this->getAccessCacheContextsForEntity($this->entity);
        $additional_cache_contexts = $this->getAdditionalCacheContextsForEntity($this->referencingEntity);
        if (count($access_cache_contexts) || count($additional_cache_contexts)) {
            $cache_contexts = Cache::mergeContexts($entity_cache_contexts, $additional_cache_contexts);
            $cache_contexts = Cache::mergeContexts($cache_contexts, $access_cache_contexts);
            $context_metadata = \Drupal::service('cache_contexts_manager')->convertTokensToKeys($cache_contexts);
            $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, $context_metadata->getCacheTags());
        }
        $this->verifyRenderCache($cache_keys, $referencing_entity_cache_tags, (new CacheableMetadata())->setCacheContexts($entity_cache_contexts));
        $this->verifyPageCache($non_referencing_entity_url, 'MISS');
        // Verify a cache hit, but also the presence of the correct cache tags.
        $this->verifyPageCache($non_referencing_entity_url, 'HIT', Cache::mergeTags($non_referencing_entity_cache_tags, $page_cache_tags));
        // Also verify the existence of an entity render cache entry.
        $cache_keys = [
            'entity_view',
            'entity_test',
            $this->nonReferencingEntity
                ->id(),
            'full',
        ];
        $this->verifyRenderCache($cache_keys, $non_referencing_entity_cache_tags, (new CacheableMetadata())->setCacheContexts($entity_cache_contexts));
        // Prime the page cache for the listing of referencing entities.
        $this->verifyPageCache($listing_url, 'MISS');
        // Verify a cache hit, but also the presence of the correct cache tags.
        $expected_tags = Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags);
        $expected_tags = Cache::mergeTags($expected_tags, $page_cache_tags_referencing_entity);
        $this->verifyPageCache($listing_url, 'HIT', $expected_tags);
        // Prime the page cache for the empty listing.
        $this->verifyPageCache($empty_entity_listing_url, 'MISS');
        // Verify a cache hit, but also the presence of the correct cache tags.
        $this->verifyPageCache($empty_entity_listing_url, 'HIT', $empty_entity_listing_cache_tags);
        // Verify the entity type's list cache contexts are present.
        $contexts_in_header = $this->getSession()
            ->getResponseHeader('X-Drupal-Cache-Contexts');
        $this->assertEqualsCanonicalizing(Cache::mergeContexts($page_cache_contexts, $this->getAdditionalCacheContextsForEntityListing()), empty($contexts_in_header) ? [] : explode(' ', $contexts_in_header));
        // Prime the page cache for the listing containing the referenced entity.
        $this->verifyPageCache($nonempty_entity_listing_url, 'MISS', $nonempty_entity_listing_cache_tags);
        // Verify a cache hit, but also the presence of the correct cache tags.
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT', $nonempty_entity_listing_cache_tags);
        // Verify the entity type's list cache contexts are present.
        $contexts_in_header = $this->getSession()
            ->getResponseHeader('X-Drupal-Cache-Contexts');
        $this->assertEqualsCanonicalizing(Cache::mergeContexts($page_cache_contexts, $this->getAdditionalCacheContextsForEntityListing()), empty($contexts_in_header) ? [] : explode(' ', $contexts_in_header));
        // Verify that after modifying the referenced entity, there is a cache miss
        // for every route except the one for the non-referencing entity.
        $this->entity
            ->save();
        $this->verifyPageCache($referencing_entity_url, 'MISS');
        $this->verifyPageCache($listing_url, 'MISS');
        $this->verifyPageCache($empty_entity_listing_url, 'MISS');
        $this->verifyPageCache($nonempty_entity_listing_url, 'MISS');
        $this->verifyPageCache($non_referencing_entity_url, 'HIT');
        // Verify cache hits.
        $this->verifyPageCache($referencing_entity_url, 'HIT');
        $this->verifyPageCache($listing_url, 'HIT');
        $this->verifyPageCache($empty_entity_listing_url, 'HIT');
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
        // Verify that after modifying the referencing entity, there is a cache miss
        // for every route except the ones for the non-referencing entity and the
        // empty entity listing.
        $this->referencingEntity
            ->save();
        $this->verifyPageCache($referencing_entity_url, 'MISS');
        $this->verifyPageCache($listing_url, 'MISS');
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
        $this->verifyPageCache($non_referencing_entity_url, 'HIT');
        $this->verifyPageCache($empty_entity_listing_url, 'HIT');
        // Verify cache hits.
        $this->verifyPageCache($referencing_entity_url, 'HIT');
        $this->verifyPageCache($listing_url, 'HIT');
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
        // Verify that after modifying the non-referencing entity, there is a cache
        // miss only for the non-referencing entity route.
        $this->nonReferencingEntity
            ->save();
        $this->verifyPageCache($referencing_entity_url, 'HIT');
        $this->verifyPageCache($listing_url, 'HIT');
        $this->verifyPageCache($empty_entity_listing_url, 'HIT');
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
        $this->verifyPageCache($non_referencing_entity_url, 'MISS');
        // Verify cache hits.
        $this->verifyPageCache($non_referencing_entity_url, 'HIT');
        if ($this->entity
            ->getEntityType()
            ->hasHandlerClass('view_builder')) {
            // Verify that after modifying the entity's display, there is a cache miss
            // for both the referencing entity, and the listing of referencing
            // entities, but not for any other routes.
            $referenced_entity_view_mode = $this->selectViewMode($this->entity
                ->getEntityTypeId());
            
            /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
            $display_repository = \Drupal::service('entity_display.repository');
            $entity_display = $display_repository->getViewDisplay($entity_type, $this->entity
                ->bundle(), $referenced_entity_view_mode);
            $entity_display->save();
            $this->verifyPageCache($referencing_entity_url, 'MISS');
            $this->verifyPageCache($listing_url, 'MISS');
            $this->verifyPageCache($non_referencing_entity_url, 'HIT');
            $this->verifyPageCache($empty_entity_listing_url, 'HIT');
            $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
            // Verify cache hits.
            $this->verifyPageCache($referencing_entity_url, 'HIT');
            $this->verifyPageCache($listing_url, 'HIT');
        }
        if ($bundle_entity_type_id = $this->entity
            ->getEntityType()
            ->getBundleEntityType()) {
            // Verify that after modifying the corresponding bundle entity, there is a
            // cache miss for both the referencing entity, and the listing of
            // referencing entities, but not for any other routes.
            $bundle_entity = $this->container
                ->get('entity_type.manager')
                ->getStorage($bundle_entity_type_id)
                ->load($this->entity
                ->bundle());
            $bundle_entity->save();
            $this->verifyPageCache($referencing_entity_url, 'MISS');
            $this->verifyPageCache($listing_url, 'MISS');
            $this->verifyPageCache($non_referencing_entity_url, 'HIT');
            // Special case: entity types may choose to use their bundle entity type
            // cache tags, to avoid having excessively granular invalidation.
            $is_special_case = $bundle_entity->getCacheTags() == $this->entity
                ->getCacheTags() && $bundle_entity->getEntityType()
                ->getListCacheTags() == $this->entity
                ->getEntityType()
                ->getListCacheTags();
            if ($is_special_case) {
                $this->verifyPageCache($empty_entity_listing_url, 'MISS');
                $this->verifyPageCache($nonempty_entity_listing_url, 'MISS');
            }
            else {
                $this->verifyPageCache($empty_entity_listing_url, 'HIT');
                $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
            }
            // Verify cache hits.
            $this->verifyPageCache($referencing_entity_url, 'HIT');
            $this->verifyPageCache($listing_url, 'HIT');
            if ($is_special_case) {
                $this->verifyPageCache($empty_entity_listing_url, 'HIT');
                $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
            }
        }
        if ($this->entity
            ->getEntityType()
            ->get('field_ui_base_route')) {
            // Verify that after modifying a configurable field on the entity, there
            // is a cache miss.
            $field_storage_name = $this->entity
                ->getEntityTypeId() . '.configurable_field';
            $field_storage = FieldStorageConfig::load($field_storage_name);
            $field_storage->save();
            $this->verifyPageCache($referencing_entity_url, 'MISS');
            $this->verifyPageCache($listing_url, 'MISS');
            $this->verifyPageCache($empty_entity_listing_url, 'HIT');
            $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
            $this->verifyPageCache($non_referencing_entity_url, 'HIT');
            // Verify cache hits.
            $this->verifyPageCache($referencing_entity_url, 'HIT');
            $this->verifyPageCache($listing_url, 'HIT');
            // Verify that after modifying a configurable field on the entity, there
            // is a cache miss.
            $field_name = $this->entity
                ->getEntityTypeId() . '.' . $this->entity
                ->bundle() . '.configurable_field';
            $field = FieldConfig::load($field_name);
            $field->save();
            $this->verifyPageCache($referencing_entity_url, 'MISS');
            $this->verifyPageCache($listing_url, 'MISS');
            $this->verifyPageCache($empty_entity_listing_url, 'HIT');
            $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
            $this->verifyPageCache($non_referencing_entity_url, 'HIT');
            // Verify cache hits.
            $this->verifyPageCache($referencing_entity_url, 'HIT');
            $this->verifyPageCache($listing_url, 'HIT');
        }
        // Verify that after invalidating the entity's cache tag directly, there is
        // a cache miss for every route except the ones for the non-referencing
        // entity and the empty entity listing.
        Cache::invalidateTags($this->entity
            ->getCacheTagsToInvalidate());
        $this->verifyPageCache($referencing_entity_url, 'MISS');
        $this->verifyPageCache($listing_url, 'MISS');
        $this->verifyPageCache($nonempty_entity_listing_url, 'MISS');
        $this->verifyPageCache($non_referencing_entity_url, 'HIT');
        $this->verifyPageCache($empty_entity_listing_url, 'HIT');
        // Verify cache hits.
        $this->verifyPageCache($referencing_entity_url, 'HIT');
        $this->verifyPageCache($listing_url, 'HIT');
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
        // Verify that after invalidating the entity's list cache tag directly,
        // there is a cache miss for both the empty entity listing and the non-empty
        // entity listing routes, but not for other routes.
        Cache::invalidateTags($this->entity
            ->getEntityType()
            ->getListCacheTags());
        $this->verifyPageCache($empty_entity_listing_url, 'MISS');
        $this->verifyPageCache($nonempty_entity_listing_url, 'MISS');
        $this->verifyPageCache($referencing_entity_url, 'HIT');
        $this->verifyPageCache($non_referencing_entity_url, 'HIT');
        $this->verifyPageCache($listing_url, 'HIT');
        // Verify cache hits.
        $this->verifyPageCache($empty_entity_listing_url, 'HIT');
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
        if (!empty($view_cache_tag)) {
            // Verify that after invalidating the generic entity type's view cache tag
            // directly, there is a cache miss for both the referencing entity, and the
            // listing of referencing entities, but not for other routes.
            Cache::invalidateTags($view_cache_tag);
            $this->verifyPageCache($referencing_entity_url, 'MISS');
            $this->verifyPageCache($listing_url, 'MISS');
            $this->verifyPageCache($non_referencing_entity_url, 'HIT');
            $this->verifyPageCache($empty_entity_listing_url, 'HIT');
            $this->verifyPageCache($nonempty_entity_listing_url, 'HIT');
            // Verify cache hits.
            $this->verifyPageCache($referencing_entity_url, 'HIT');
            $this->verifyPageCache($listing_url, 'HIT');
        }
        // Verify that after deleting the entity, there is a cache miss for every
        // route except for the non-referencing entity one.
        $this->entity
            ->delete();
        $this->verifyPageCache($referencing_entity_url, 'MISS');
        $this->verifyPageCache($listing_url, 'MISS');
        $this->verifyPageCache($empty_entity_listing_url, 'MISS');
        $this->verifyPageCache($nonempty_entity_listing_url, 'MISS');
        $this->verifyPageCache($non_referencing_entity_url, 'HIT');
        // Verify cache hits.
        $referencing_entity_cache_tags = Cache::mergeTags($this->referencingEntity
            ->getCacheTags(), \Drupal::entityTypeManager()->getViewBuilder('entity_test')
            ->getCacheTags());
        $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags, [
            'http_response',
            'rendered',
        ]);
        $nonempty_entity_listing_cache_tags = Cache::mergeTags($this->entity
            ->getEntityType()
            ->getListCacheTags(), $this->getAdditionalCacheTagsForEntityListing());
        $nonempty_entity_listing_cache_tags = Cache::mergeTags($nonempty_entity_listing_cache_tags, $page_cache_tags);
        $this->verifyPageCache($referencing_entity_url, 'HIT', Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags));
        $this->verifyPageCache($listing_url, 'HIT', $page_cache_tags);
        $this->verifyPageCache($empty_entity_listing_url, 'HIT', $empty_entity_listing_cache_tags);
        $this->verifyPageCache($nonempty_entity_listing_url, 'HIT', $nonempty_entity_listing_cache_tags);
    }
    
    /**
     * Verify that a given render cache entry exists, with the correct cache tags.
     *
     * @param string[] $keys
     *   The render cache item keys.
     * @param array $tags
     *   An array of expected cache tags.
     * @param \Drupal\Core\Cache\CacheableDependencyInterface $cacheability
     *   The initial cacheability the item was rendered with.
     */
    protected function verifyRenderCache(array $keys, array $tags, CacheableDependencyInterface $cacheability) {
        $cache_bin = $this->getRenderCacheBackend();
        // Also verify the existence of an entity render cache entry.
        $cache_entry = $cache_bin->get($keys, $cacheability);
        $this->assertInstanceOf(\stdClass::class, $cache_entry);
        sort($cache_entry->tags);
        sort($tags);
        $this->assertSame($cache_entry->tags, $tags);
    }
    
    /**
     * Retrieves the render cache backend as a variation cache.
     *
     * This is how Drupal\Core\Render\RenderCache uses the render cache backend.
     *
     * @return \Drupal\Core\Cache\VariationCacheInterface
     *   The render cache backend as a variation cache.
     */
    protected function getRenderCacheBackend() {
        
        /** @var \Drupal\Core\Cache\VariationCacheFactoryInterface $variation_cache_factory */
        $variation_cache_factory = \Drupal::service('variation_cache_factory');
        return $variation_cache_factory->get('render');
    }

}