yii\web\CacheSession::writeSession PHP Method

    public function writeSession($id, $data)
    {
        return $this->cache->set($this->calculateKey($id), $data, $this->getTimeout());
    }

 public function testCacheSession()
 {
     $session = new CacheSession();
     $session->writeSession('test', 'sessionData');
     $this->assertEquals('sessionData', $session->readSession('test'));
     $session->destroySession('test');
     $this->assertEquals('', $session->readSession('test'));
 }