silverstripe-framework/tests/php/Control/FakeController.php

<?php

namespace SilverStripe\Control\Tests;

use SilverStripe\Control\Session;
use SilverStripe\Core\Injector\Injector;
use SilverStripe\Control\HTTPRequest;
use SilverStripe\Control\HTTPResponse;
use SilverStripe\Control\Controller;

// Fake a current controller. Way harder than it should be
class FakeController extends Controller
{

    public function __construct()
    {
        parent::__construct();

        $session = Injector::inst()->create(Session::class, isset($_SESSION) ? $_SESSION : array());
        $this->setSession($session);

        $this->pushCurrent();

        $request = new HTTPRequest(
            (isset($_SERVER['X-HTTP-Method-Override']))
                ? $_SERVER['X-HTTP-Method-Override']
                : $_SERVER['REQUEST_METHOD'],
            '/'
        );
        $this->setRequest($request);

        $this->setResponse(new HTTPResponse());

        $this->doInit();
    }
}