use fixed timestamp to avoid test failures, fixes #2522

Closes #2522

Merge request studip/studip!1711

tests/jsonapi/UserScheduleShowTest.php

@@ -44,6 +44,7 @@ class UserScheduleShowTest extends \Codeception\Test\Unit
 
         $requestBuilder = $this->tester->createRequestBuilder($credentials);
         $requestBuilder->setUri('/users/'.$credentials['id'].'/schedule')->fetch();
+        $requestBuilder->setUriQueryParam('filter[timestamp]', Semester::findOneBySQL('1')->beginn);
 
         $response = $this->tester->sendMockRequest($app, $requestBuilder->getRequest());
         $this->tester->assertTrue($response->isSuccessfulDocument([200]));