magento-test/app/code/Magento/SendFriend/view/frontend/web/requirejs-config.js

/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
var config = {
    map: {
        '*': {
            'Magento_SendFriend/back-event': 'Magento_SendFriend/js/back-event'
        }
    }
};