Neos\Flow\Session\Session::putData PHP Method

    public function putData($key, $data)
    {
        if ($this->started !== true) {
            throw new Exception\SessionNotStartedException('Tried to create a session data entry, but the session has not been started yet.', 1351162259);
        }
        if (is_resource($data)) {
            throw new Exception\DataNotSerializableException('The given data cannot be stored in a session, because it is of type "' . gettype($data) . '".', 1351162262);
        }
        $this->storageCache->set($this->storageIdentifier . md5($key), $data, [$this->storageIdentifier], 0);
    }

 /**
  * @test
  * @expectedException \Neos\Flow\Session\Exception\SessionNotStartedException
  */
 public function putDataThrowsExceptionIfSessionIsNotStarted()
 {
     $session = new Session();
     $session->putData('some key', 'some value');
 }