Unable to test localized widget in flutter when using .json files. #45166
Description
#22193 (comment)
@chunhtai actually it doesn't work.
In our case, we are using .json files to do translations. So we have like these:
- assets/lang/en.json
- assets/lang/pt.json
- assets/lang/es.json
.....
The way we load and use these json files are through LocalizationsDelegate extension like this:
class AppLocalizations {
final Locale locale;
AppLocalizations(this.locale);
static AppLocalizations of(BuildContext context) =>
Localizations.of<AppLocalizations>(context, AppLocalizations);
static const LocalizationsDelegate<AppLocalizations> delegate =
_AppLocalizationsDelegate();
Map<String, String> _localizedStrings;
Future<bool> load() async {
try {
String jsonString = await rootBundle.loadString('assets/lang/${locale.languageCode}.json'); **here is the problem**
Map<String, dynamic> jsonMap = json.decode(jsonString);
_localizedStrings = jsonMap.map((key, value) => MapEntry(key, value));
return true;
} catch (e) {
return false;
}
}
String translate(String key) => _localizedStrings[key];
}
class _AppLocalizationsDelegate
extends LocalizationsDelegate<AppLocalizations> {
const _AppLocalizationsDelegate();
@override
bool isSupported(Locale locale) {
return ['en', 'pt', 'es'].contains(locale.languageCode);
}
@override
Future<AppLocalizations> load(Locale locale) async {
AppLocalizations localizations = AppLocalizations(locale);
await localizations.load();
return localizations;
}
@override
bool shouldReload(LocalizationsDelegate<AppLocalizations> old) => false;
}
class MyTranslatedWidget extends StatefulWidget {
@override
_MyTranslatedWidgetState createState() => _MyTranslatedWidgetState();
}
class _MyTranslatedWidget extends State<MyTranslatedWidget> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Text(
AppLocalizations.of(context).translate('hello_key'),
),
);
}
}
and then in our widget test, we have something like this:
testWidgets(
'my test description',
(WidgetTester tester) async {
await tester.runAsync(() async {
await tester.pumpWidget(MaterialApp(
locale: Locale('en'),
localizationsDelegates: [
GlobalMaterialLocalizations.delegate,
GlobalWidgetsLocalizations.delegate,
AppLocalizations.delegate **here is the problem**
],
home: MyTranslatedWidget(),
));
final titleFinder = find.text('hello');
expect(titleFinder, findsOneWidget);
});
},
);
After running this test we got the following problem:
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following TestFailure object was thrown while running async test code:
Expected: exactly one matching node in the widget tree
Actual: ?:<zero widgets with text "hello" (ignoring offstage widgets)>
Which: means none were found but one was expected
This happens because,AppLocalizations.delegate that is called on localizationsDelegates from MaterialApp is not able to load the .json file that have all the text translations.
Something happens here: String jsonString = await rootBundle.loadString('assets/lang/${locale.languageCode}.json');
it seems like the rootBundle can't find or load the json assets...