chore(tests): Cleanup bootstrap.php to be forward-compatible

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

Author: come-nc

tests/unit/bootstrap.php

@@ -1,17 +1,27 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2016 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
+use OCP\App\IAppManager;
+use OCP\Server;
+use PHPUnit\Framework\TestCase;
+
 if (!defined('PHPUNIT_RUN')) {
 	define('PHPUNIT_RUN', 1);
 }
+
 require_once __DIR__ . '/../../../../lib/base.php';
-\OC::$loader->addValidRoot(\OC::$SERVERROOT . '/tests');
-\OC_App::loadApp('user_saml');
-if (!class_exists(\PHPUnit\Framework\TestCase::class)) {
+require_once __DIR__ . '/../../../../tests/autoload.php';
+
+Server::get(IAppManager::class)->loadApp('user_saml');
+
+if (!class_exists(TestCase::class)) {
 	require_once('PHPUnit/Autoload.php');
 }
+
 OC_Hook::clear();