YOURLS/tests/data/plugins/test-plugin/uninstall.php

<?php
/**
 * Uninstall script
 * This file is executed when the plugin is uninstalled on YOURLS 1.8.3 or later.
 */

// No direct call.
if( !defined( 'YOURLS_UNINSTALL_PLUGIN' ) ) die();

// The uninstallation process itself

// Nothing.