Custom library config file

I have a feeling the require_once "config.php" may be part of the issue, but if you can't change the API code, there's only so much you can do. Have you tried using the instance created by the loader:

PHP Code:

$this->libapi->doSomething('.TXT', 1); 


instead of this:

PHP Code:

$api = new LibAPI();
$api->doSomething('.TXT', 1); 


Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide