Grav/tests/_bootstrap.php

<?php
namespace Grav;

use Codeception\Util\Fixtures;
use Faker\Factory;
use Grav\Common\Grav;

ini_set('error_log', __DIR__ . '/error.log');

$grav = function() {
    Grav::resetInstance();
    $grav = Grav::instance();

    $grav['uri']->init();
    $grav['debugger']->init();
    $grav['assets']->init();
    $grav['config']->set('system.cache.enabled', false);
    $grav['locator']->addPath('tests', '', 'tests', false);

    return $grav;
};

Fixtures::add('grav', $grav);

$fake = Factory::create();
Fixtures::add('fake', $fake);