Flutter，如何对包含 AppLocalization（多语言）的 Widget 进行单元测试？

Question

我正在尝试对我的 HistoryPage 小部件进行简单测试，这里是：

class HistoryPage extends StatefulWidget {
  @override
  _HistoryPageState createState() => _HistoryPageState();
}

class _HistoryPageState extends State<HistoryPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(AppLocalizations.of(context)!.historyPageTitle),
        backgroundColor: Colors.green,
      ),
      body: Column(
        children: [
        ],
      ),
    );
  }
}

这是该小部件的单元测试：

  group('UI TESTS', () {
    Widget makeTesteableWidget({required Widget child}) {
      return MaterialApp(
        home: child,
      );
    }

    testWidgets('History page', (WidgetTester tester) async {
      // Create the widget by telling the tester to build it.
      final widget = makeTesteableWidget(
        child: HistoryPage(),
      );

      await tester.pumpWidget(widget);

      expect(true, true);
    });
  });

这是我运行测试时的异常：

══╡ 小部件库发现异常╞═══════════════════════╕═══╕═␕═════════════════ ═════════════════════ 以下 _CastError 被抛出构建 HistoryPage(dirty, dependencies: [_LocalizationsScope-[GlobalKey#ca13b]]，状态：_HistoryPageState#b1cad）： 用于空值的空检查运算符

如果我像这样替换 AppBar 标题：

appBar: AppBar(
            title: Text('Simple title'),
            backgroundColor: Colors.green,
          ),

测试正在运行...但我不知道如何管理此行以不引发此异常...

title: Text(AppLocalizations.of(context)!.historyPageTitle),

感谢您的帮助！

Answer 1

发现问题！在测试中，在 MaterialApp 中，我刚刚调用了本地化（就像在主程序中一样），如下所示：

group('UI TESTS', () {
    Widget makeTesteableWidget({required Widget child}) {
      return MaterialApp(
        localizationsDelegates: [
          AppLocalizations.delegate,
          GlobalMaterialLocalizations.delegate,
          GlobalWidgetsLocalizations.delegate,
          GlobalCupertinoLocalizations.delegate,
        ],
        supportedLocales: [
          const Locale('en', ''),
          // English, no country code
          const Locale('fr', ''),
          // French, no country code
          const Locale('de', ''),
          // German, no country code
          // const Locale('gsw', ''), // Swiss German Alemannic Alsatian, no country code
          const Locale('it', ''),
          // Italian, no country code
        ],
        home: child,
      );
    }

    testWidgets('History page', (WidgetTester tester) async {
      // Create the widget by telling the tester to build it.
      final widget = makeTesteableWidget(
        child: LoginPage(),
      );

      await tester.pumpWidget(widget);

      expect(true, true);
    });
  });