Testing

intento hacer testing de mis controladores pero no logro conectar a la base de datos de test
me sale ese error:
1) CodeIgniter\TestSliderController::testIndex
CodeIgniter\Database\Exceptions\DatabaseException: Unable to connect to the database.
Main connection [MySQLi]: php_network_getaddresses: getaddrinfo failed: nodename nor servname provided, or not known


Esta es mi config en Database.php
public $default = [
        'DSN'      => '',
        'hostname' => 'localhost',
        'username' => 'root',
        'password' => 'root',
        'database' => 'mi_base_de_datos',
        'DBDriver' => 'MySQLi',
        'DBPrefix' => '',
        'pConnect' => false,
        'DBDebug'  => (ENVIRONMENT !== 'production'),
        'charset'  => 'utf8',
        'DBCollat' => 'utf8_general_ci',
        'swapPre'  => '',
        'encrypt'  => false,
        'compress' => false,
        'strictOn' => false,
        'failover' => [],
        'port'    => 3306,
    ];

    public $tests = [
        'DSN'      => '',
        public $default = [
        'DSN'      => '',
        'hostname' => 'localhost',
        'username' => 'root',
        'password' => 'root',
        'database' => 'test',
        'DBDriver' => 'MySQLi',
        'DBPrefix' => '',
        'pConnect' => false,
        'DBDebug'  => (ENVIRONMENT !== 'production'),
        'charset'  => 'utf8',
        'DBCollat' => 'utf8_general_ci',
        'swapPre'  => '',
        'encrypt'  => false,
        'compress' => false,
        'strictOn' => false,
        'failover' => [],
        'port'    => 3306,
    ];