materio-base-d7/modules/image/tests/image_module_test.module

<?php

/**
 * @file
 * Provides Image module hook implementations for testing purposes.
 */

function image_module_test_file_download($uri) {
  if (variable_get('image_module_test_file_download', FALSE) == $uri) {
    return array('X-Image-Owned-By' => 'image_module_test');
  }
  return -1;
}

/**
 * Implements hook_image_effect_info().
 */
function image_module_test_image_effect_info() {
  $effects = array(
    'image_module_test_null' => array(
    'effect callback' => 'image_module_test_null_effect',
    ),
  );

  return $effects;
}

/**
 * Image effect callback; Null.
 *
 * @param $image
 *   An image object returned by image_load().
 * @param $data
 *   An array with no attributes.
 *
 * @return
 *   TRUE
 */
function image_module_test_null_effect(array &$image, array $data) {
  return TRUE;
}