docker-speedtest-server/speedtest/speedtest/empty.php

<?php
header( "HTTP/1.1 200 OK" );
header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");
header("Connection: keep-alive");
?>