createCacheId example

$render_cache_tag = 'rendered';

    $this->verifyPageCache($entity_url, 'MISS');

    // Verify a cache hit, but also the presence of the correct cache tags.     $this->verifyPageCache($entity_url, 'HIT');

    // Also verify the existence of an entity render cache entry, if this entity     // type supports render caching.     if (\Drupal::entityTypeManager()->getDefinition($entity_type)->isRenderCacheable()) {
      $cache_keys = ['entity_view', $entity_type, $this->entity->id(), $view_mode];
      $cid = $this->createCacheId($cache_keys, $entity_cache_contexts);
      $redirected_cid = NULL;
      $additional_cache_contexts = $this->getAdditionalCacheContextsForEntity($this->entity);
      if (count($additional_cache_contexts)) {
        $redirected_cid = $this->createCacheId($cache_keys, Cache::mergeContexts($entity_cache_contexts, $additional_cache_contexts));
      }
      $expected_cache_tags = Cache::mergeTags($cache_tag, $view_cache_tag);
      $expected_cache_tags = Cache::mergeTags($expected_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
      $expected_cache_tags = Cache::mergeTags($expected_cache_tags, [$render_cache_tag]);
      $this->verifyRenderCache($cid, $expected_cache_tags, $redirected_cid);
    }

    

$expected_block_cache_contexts = ['languages:' . LanguageInterface::TYPE_INTERFACE, 'theme', 'user.permissions'];
    $expected_block_cache_tags = Cache::mergeTags(['block_view', 'rendered'], $block->getCacheTags());
    $expected_block_cache_tags = Cache::mergeTags($expected_block_cache_tags, $block->getPlugin()->getCacheTags());

    // Expected contexts and tags for the BlockContent entity.     // @see \Drupal\Core\Entity\EntityViewBuilder::getBuildDefaults().     $expected_entity_cache_contexts = ['theme'];
    $expected_entity_cache_tags = Cache::mergeTags(['block_content_view'], $this->entity->getCacheTags());
    $expected_entity_cache_tags = Cache::mergeTags($expected_entity_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));

    // Verify that what was render cached matches the above expectations.     $cid = $this->createCacheId($expected_block_cache_keys, $expected_block_cache_contexts);
    $redirected_cid = $this->createCacheId($expected_block_cache_keys, Cache::mergeContexts($expected_block_cache_contexts, $expected_entity_cache_contexts));
    $this->verifyRenderCache($cid, Cache::mergeTags($expected_block_cache_tags, $expected_entity_cache_tags), ($cid !== $redirected_cid) ? $redirected_cid : NULL);
  }

}

$nonempty_entity_listing_cache_tags = Cache::mergeTags($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'];
    $cid = $this->createCacheId($cache_keys, $entity_cache_contexts);
    $access_cache_contexts = $this->getAccessCacheContextsForEntity($this->entity);
    $additional_cache_contexts = $this->getAdditionalCacheContextsForEntity($this->referencingEntity);
    $redirected_cid = NULL;
    if (count($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);
      $redirected_cid = $this->createCacheId($cache_keys, $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());
    }
    $this->verifyRenderCache($cid, $referencing_entity_cache_tags, $redirected_cid);