chore: add integration tests for user language settings (#3560)

frontend/appflowy_flutter/integration_test/runner.dart

@@ -22,6 +22,8 @@ import 'tabs_test.dart' as tabs_test;
 import 'hotkeys_test.dart' as hotkeys_test;
 import 'appearance_settings_test.dart' as appearance_test_runner;
 import 'auth/auth_test.dart' as auth_test_runner;
+import 'settings/user_icon_test.dart' as user_icon_test;
+import 'settings/user_language_test.dart' as user_language_test;
 
 /// The main task runner for all integration tests in AppFlowy.
 ///
@@ -67,6 +69,10 @@ void main() {
   // Appearance integration test
   appearance_test_runner.main();
 
+  // User settings
+  user_icon_test.main();
+  user_language_test.main();
+
   if (isSupabaseEnabled) {
     auth_test_runner.main();
   }

frontend/appflowy_flutter/integration_test/settings/user_language_test.dart

@@ -0,0 +1,69 @@
+import 'dart:ui';
+
+import 'package:appflowy/workspace/presentation/settings/widgets/settings_language_view.dart';
+import 'package:integration_test/integration_test.dart';
+import 'package:flutter_test/flutter_test.dart';
+import '../util/util.dart';
+import 'package:appflowy/workspace/application/settings/prelude.dart';
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  group('Settings: user language tests', () {
+    testWidgets('select language, language changed', (tester) async {
+      await tester.initializeAppFlowy();
+
+      await tester.tapGoButton();
+      tester.expectToSeeHomePage();
+      await tester.openSettings();
+
+      await tester.openSettingsPage(SettingsPage.language);
+
+      final userLanguageFinder = find.descendant(
+        of: find.byType(SettingsLanguageView),
+        matching: find.byType(LanguageSelector),
+      );
+
+      // Grab current locale
+      LanguageSelector userLanguage =
+          tester.widget<LanguageSelector>(userLanguageFinder);
+      Locale currentLocale = userLanguage.currentLocale;
+
+      // Open language selector
+      await tester.tap(userLanguageFinder);
+      await tester.pumpAndSettle();
+
+      // Select first option that isn't default
+      await tester.tap(find.byType(LanguageItem).at(1));
+      await tester.pumpAndSettle();
+
+      // Make sure the new locale is not the same as previous one
+      userLanguage = tester.widget<LanguageSelector>(userLanguageFinder);
+      expect(
+        userLanguage.currentLocale,
+        isNot(equals(currentLocale)),
+        reason: "new language shouldn't equal the previous selected language",
+      );
+
+      // Update the current locale to a new one
+      currentLocale = userLanguage.currentLocale;
+
+      // Tried the same flow for the second time
+      // Open language selector
+      await tester.tap(userLanguageFinder);
+      await tester.pumpAndSettle();
+
+      // Select second option that isn't default
+      await tester.tap(find.byType(LanguageItem).at(2));
+      await tester.pumpAndSettle();
+
+      // Make sure the new locale is not the same as previous one
+      userLanguage = tester.widget<LanguageSelector>(userLanguageFinder);
+      expect(
+        userLanguage.currentLocale,
+        isNot(equals(currentLocale)),
+        reason: "new language shouldn't equal the previous selected language",
+      );
+    });
+  });
+}