tester-1.0.0/modules/tester_error_generator/tester_error_generator.module

<?php

/**
 * @file
 * A small module that deliberately throws errors.
 */

use Drupal\tester_error_generator\TesterErrorClass;

/**
 * Implements hook_page_top().
 *
 * In this function, we insert deliberate errors under some conditions.
 */
function tester_error_generator_page_top(&$page_top) {
  // Get the current request path.
  $path = \Drupal::request()->getPathInfo();
  // Always throw a warning on /, otherwise, randomize.
  $number = ($path === '/') ? 1 : (int) ceil(rand(1, 8));
  switch ($number) {
    case 1:
      $text = t('Generate a warning');
      trigger_error($text, E_USER_WARNING);
      break;

    case 2:
      $text = t('Generate an error');
      trigger_error($text, E_USER_ERROR);
      break;

    case 3:
      $text = t('Generate a deprecation');
      @trigger_error($text, E_USER_DEPRECATED);
      break;

    case 4:
      $text = t('Generate class errors');
      $testcase = new TesterErrorClass();
      $testcase->testDynamicProperty();
      break;

    default:
      $text = t('The <em>tester_error_generator</em> module should not be used in production');
      break;
  }

  // Do not cache our result.
  return $page_top['tester'] = [
    '#prefix' => '<div class="messages messages--warning">',
    '#markup' => $text,
    '#suffix' => '</div>',
    '#cache' => ['max-age' => 0],
  ];
}