code: protected function persistCacheEntry($key)
      {
          $success = true;
          if (isset($this->cache[$key])) {
              $cache = $this->cache[$key];
  
              switch ($cache['state']) {
                  case self::STATE_PENDING_WRITE:
                      $success = $this->getStorage()->set($cache['userId'], $cache['callId'], $cache['data']);
                      if (!$success) {
                          throw new \common_exception_Error('Can\'t write into test runner state storage at '.static::class);
                      }
                      $this->cache[$key]['state'] = self::STATE_ALIGNED;
                      break;
  
                  case self::STATE_PENDING_DELETE:
                      $success = $this->getStorage()->del($cache['userId'], $cache['callId']);
                      if ($success) {
                          unset($this->cache[$key]);
                      }
                      break;
              }
          }
          return $success;
      }
docs: Persists a cache entry and update its status.
  
  @param string $key
  @return bool