You can use an internal rewrite instead of .htaccess:
function wpd_service_rewrite() {
add_rewrite_rule(
'^service/testing-tool/([a-z0-9.]+)$',
'index.php?pagename=service/results',
'top'
);
}
add_action( 'init', 'wpd_service_rewrite' );
Don’t forget to flush rewrite rules after adding / changing them.