How to use Forge Class to create a database schema?

I'm using CodeIgniter 3.1.0 to develop an app. In order to improve installation, I've written an Install_Controller, and an Install_Model.
I want to use Database Forge class to manage the database schema, but it's not very clear in user guide and nothing on Google helps.
I need to use $this->dbforge->create_database, because the user knows nothing about database, so all he will do is MySQL "Next, next, install" and then run a Windows batch file that run PHP as web server, so from Chrome he can use URL to install the app.

User guide says: In order to initialize the Forge class, your database driver must already be running, since the forge class relies on it.

So I have setup the config/database.php with user, pwd, dbname and so on... Even because I need it to use in app. That's working fine in app.

After I delete my database to start over from a fresh install and try to load the Install URL, give me the error: Message: mysqli::real_connect(): (HY000/1049): Unknown database 'test'

So, how can I use Forge Class to create database schema, if I need to have it first?

Some code...

Code:

$db['default'] = array(
   'dsn' => '',
   'hostname' => 'localhost',
   'username' => 'root',
   'password' => 'root',
   'database' => 'test',
   'dbdriver' => 'mysqli'
);

$autoload['libraries'] = array('database');

class Install extends CI_Controller
{
   public function __construct()
   {
       parent::__construct();
   }

   public function index()
   {
       $this->load->model('install_model');
       $this->install_model->createDabase();
   }
}

class Install_model extends CI_Model {
   function __construct() {
       parent::__construct();
   }

   function createDabase() {
       $this->load->dbforge();

       if ($this->dbforge->create_database('test'))
           echo 'Database created!';
       else
           echo 'Database error!';
   }
}

I made a very dirty workaround, I hope someone give me a nice answer...
1. Remove database from autoloader.
2. Use multiple databases, the default one is the same, but I created a second one having empty database name.
3. Use the second database with Forge Class, instead of the default until create schema, then I back to the default to create tables.
4. Load manually the default database in others Controllers