drupal/modules/update/tests/update_test.module

<?php

/**
 * Implements hook_menu().
 */
function update_test_menu() {
  $items = array();

  $items['update-test'] = array(
    'title' => t('Update test'),
    'page callback' => 'update_test_mock_page',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
  $items['503-error'] = array(
    'title' => t('503 Service unavailable'),
    'page callback' => 'update_callback_service_unavailable',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );

  return $items;
}

/**
 * Implements hook_system_info_alter().
 *
 * This checks the 'update_test_system_info' variable and sees if we need to
 * alter the system info for the given $file based on the setting. The setting
 * is expected to be a nested associative array. If the key '#all' is defined,
 * its subarray will include .info keys and values for all modules and themes
 * on the system. Otherwise, the settings array is keyed by the module or
 * theme short name ($file->name) and the subarrays contain settings just for
 * that module or theme.
 */
function update_test_system_info_alter(&$info, $file) {
  $setting = variable_get('update_test_system_info', array());
  foreach (array('#all', $file->name) as $id) {
    if (!empty($setting[$id])) {
      foreach ($setting[$id] as $key => $value) {
        $info[$key] = $value;
      }
    }
  }
}

/**
 * Implements hook_update_status_alter().
 *
 * This checks the 'update_test_update_status' variable and sees if we need to
 * alter the update status for the given project based on the setting. The
 * setting is expected to be a nested associative array. If the key '#all' is
 * defined, its subarray will include .info keys and values for all modules
 * and themes on the system. Otherwise, the settings array is keyed by the
 * module or theme short name and the subarrays contain settings just for that
 * module or theme.
 */
function update_test_update_status_alter(&$projects) {
  $setting = variable_get('update_test_update_status', array());
  if (!empty($setting)) {
    foreach ($projects as $project_name => &$project) {
      foreach (array('#all', $project_name) as $id) {
        if (!empty($setting[$id])) {
          foreach ($setting[$id] as $key => $value) {
            $project[$key] = $value;
          }
        }
      }
    }
  }
}

/**
 * Page callback, prints mock XML for the update module.
 *
 * The specific XML file to print depends on two things: the project we're
 * trying to fetch data for, and the desired "availability scenario" for that
 * project which we're trying to test. Before attempting to fetch this data
 * (by checking for updates on the available updates report), callers need to
 * define the 'update_test_xml_map' variable as an array, keyed by project
 * name, indicating which availability scenario to use for that project.
 *
 * @param $project_name
 *   The project short name update.module is trying to fetch data for (the
 *   fetch URLs are of the form: [base_url]/[project_name]/[core_version]).
 */
function update_test_mock_page($project_name) {
  $xml_map = variable_get('update_test_xml_map', FALSE);
  if (isset($xml_map[$project_name])) {
    $availability_scenario = $xml_map[$project_name];
  }
  elseif (isset($xml_map['#all'])) {
    $availability_scenario = $xml_map['#all'];
  }
  else {
    // The test didn't specify (for example, the webroot has other modules and
    // themes installed but they're disabled by the version of the site
    // running the test. So, we default to a file we know won't exist, so at
    // least we'll get an empty page from readfile instead of a bunch of
    // Drupal page output.
    $availability_scenario = '#broken#';
  }

  $path = drupal_get_path('module', 'update_test');
  readfile("$path/$project_name.$availability_scenario.xml");
}

/**
 * Implement hook_archiver_info().
 */
function update_test_archiver_info() {
  return array(
    'update_test_archiver' => array(
      // This is bogus, we only care about the extensions for now.
      'class' => 'ArchiverUpdateTest',
      'extensions' => array('update-test-extension'),
    ),
  );
}

/**
 * Implements hook_filetransfer_info().
 */
function update_test_filetransfer_info() {
  // Define a mock file transfer method, to ensure that there will always be
  // at least one method available in the user interface (regardless of the
  // environment in which the update manager tests are run).
  return array(
    'system_test' => array(
      'title' => t('Update Test FileTransfer'),
      // This should be in an .inc file, but for testing purposes, it is OK to
      // leave it in the main module file.
      'file' => 'update_test.module',
      'class' => 'UpdateTestFileTransfer',
      'weight' => -20,
    ),
  );
}

/**
 * Mock FileTransfer object to test the settings form functionality.
 */
class UpdateTestFileTransfer {
  public static function factory() {
    return new UpdateTestFileTransfer;
  }

  public function getSettingsForm() {
    $form = array();
    $form['udpate_test_username'] = array(
      '#type' => 'textfield',
      '#title' => t('Update Test Username'),
    );
    return $form;
  }
}

/**
 * Return an Error 503 (Service unavailable) page.
 */
function update_callback_service_unavailable() {
  drupal_add_http_header('Status', '503 Service unavailable');
  print "503 Service Temporarily Unavailable";
}