changeSiteLang.js

/**
 * WordPress dependencies
 */
import { visitAdminPage, switchUserToAdmin, switchUserToTest } from '@wordpress/e2e-test-utils';

/**
 * Visits general settings page and changes the language to the given vaule.
 *
 * @param {string} lang Value of the language to set.
 *
 * @return {string} Value of the previous language.
 */
export async function changeSiteLang(lang) {
	await switchUserToAdmin();
	await visitAdminPage('options-general.php');

	const oldLang = await page.$eval(
		'#WPLANG',
		(element) => element.options[element.selectedIndex].text
	);
	await page.select('#WPLANG', lang);
	await Promise.all([
		page.click('#submit')
	]);

	await switchUserToTest();

	return oldLang;
}