prepareSiteNameUpdate example

$name = 'system.site';
    $dynamic_name = 'config_test.dynamic.new';
    /** @var \Drupal\Core\Config\StorageInterface $sync */
    $sync = $this->container->get('config.storage.sync');

    $this->drupalGet('admin/config/development/configuration');
    $this->assertSession()->pageTextContains('The staged configuration is identical to the active configuration.');
    $this->assertSession()->buttonNotExists('Import all');

    // Create updated configuration object.     $new_site_name = 'Config import test ' . $this->randomString();
    $this->prepareSiteNameUpdate($new_site_name);
    $this->assertTrue($sync->exists($name), $name . ' found.');

    // Create new config entity.     $original_dynamic_data = [
      'uuid' => '30df59bd-7b03-4cf7-bb35-d42fc49f0651',
      'langcode' => \Drupal::languageManager()->getDefaultLanguage()->getId(),
      'status' => TRUE,
      'dependencies' => [],
      'id' => 'new',
      'label' => 'New',
      'weight' => 0,