Add acceptance test for switching languages

[MAILPOET-4147]

mailpoet/tests/acceptance/Misc/SwitchingLanguagesCest.php

@@ -0,0 +1,58 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\Test\Acceptance;
+
+use AcceptanceTester;
+use Codeception\Exception\ElementNotFound;
+use Throwable;
+
+class SwitchingLanguagesCest {
+  public function switchLanguage(AcceptanceTester $i): void {
+    $i->login();
+
+    $i->wantTo('Switch WordPress language to German');
+    $i->amOnAdminPage('/options-general.php');
+    $i->selectOption('WPLANG', ['value' => 'de_DE']);
+    $i->click('[name="submit"]');
+
+    $i->wantTo('Update translations to make sure strings are downloaded');
+    $i->amOnAdminPage('/update-core.php');
+    $i->waitForText('WordPress-Aktualisierungen');
+    try {
+      $i->click('Übersetzungen aktualisieren');
+      $i->waitForText('Weiter zur WordPress-Aktualisierungs-Seite');
+    } catch (ElementNotFound $e) {
+      // translations are already up-to-date
+    }
+
+    $i->wantTo('Check menu strings (translated in PHP)');
+    $i->amOnMailpoetPage('newsletters');
+    $i->waitForText('E-Mails');
+    $i->waitForText('Automatisierungen');
+    $i->waitForText('Formulare');
+    $i->waitForText('Abonnenten');
+    $i->waitForText('Listen');
+    $i->waitForText('Einstellungen');
+    $i->waitForText('Hilfe');
+
+    $i->wantTo('Check email listing strings (translated with MailPoet.i18n)');
+    $i->waitForText('Newsletter');
+    $i->waitForText('Willkommens-E-Mail');
+    $i->waitForText('Benachrichtigung über neueste Beiträge');
+    $i->waitForText('Wiederaufnahme-E-Mails');
+
+    $i->wantTo('Check automation templates strings (translated with @wordpress/i18n)');
+    $i->amOnMailpoetPage('automation-templates');
+    $i->waitForText('Wähle dein Automatisierungstemplate');
+    $i->waitForText('Von Grund');
+    $i->waitForText('Von Grund auf neu erstellen');
+  }
+
+  public function _after(AcceptanceTester $i) {
+    try {
+      $i->cli(['language', 'core', 'uninstall', 'de_DE']);
+    } catch (Throwable $e) {
+      // language already uninstalled
+    }
+  }
+}