connect mysql database with adodb in phpunit?

Test file in phpunit don't connect to mysql using adodb. The code:

public function getConnection() {
    $HOST = "127.0.0.1";
    $USERNAME = "username";
    $PASSWORD = 'password';
    $DBTYPE = "mysqli";
    $dbName = "DBName";

    $this->db = ADONewConnection($DBTYPE);
    $this->db->debug = true;
    $this->db->Connect($HOST, $USERNAME, $PASSWORD, $dbName) or die("Unable to connect!");
}

The response:

127.0.0.1: Missing extension for mysql
Unable to connect!

Why is not posible the connection? What is wrong in the code? please help.