Operations on File object never finishing during unit tests with Flutter - flutter

Question

I'm writing unit tests for my Flutter app and I'm having some trouble when reading a json file. I have some json files that are used by my api mock class. Whenever I call a method on the File object, it never ends, but the test continues to execute, ending in an error because it didn't receive the data from the file object. It's very weird because it only happens when the mock api method is called from a provider that is called from a widget. If I call the mock api method directly my test, it works fine.
The structure of my app is as follows: WidgetScreen calls -> provider calls -> mockApi.
The Widget LegislacaoScreen calls the method carregarLegislacao from my provider, that in turn calls the method getLegislacoes from my mockApi, that method reads from a json file and returns the results to the provider that then notifies my widget. Any help is appreciated.
Oh and I'm running my tests with the command: flutter test test/my_test.dart
Here some code:
LegislacaoScreen:
class LegislacaoScreen extends StatefulWidget {
#override
_LegislacaoScreenState createState() => _LegislacaoScreenState();
}
class _LegislacaoScreenState extends State<LegislacaoScreen>
with AutomaticKeepAliveClientMixin {
#override
void initState() {
super.initState();
Future.microtask(carregarDados);
}
#override
bool get wantKeepAlive => true;
Future<void> carregarDados({bool reset = false}) async {
try {
final legislacaoProvider =
Provider.of<LegislacaoProvider>(context, listen: false);
await legislacaoProvider.carregarLegislacao(
page: legislacaoProvider.currentPage + 1,
reset: reset,
);
} catch (err) {}
}
Widget renderBody(legislacaoProvider) {
if (legislacaoProvider.carregandoLegislacao &&
legislacaoProvider.legislacoes.isEmpty &&
!legislacaoProvider.reseting) {
return Center(
child: CircularProgressIndicator(),
);
}
if (legislacaoProvider.erroCarregandoLegislacao) {
return MensagemAcao(
mensagem:
'Houve um erro ao carregar os dados.\nPor favor tente novamente.',
acao: () => carregarDados(reset: true),
);
}
return LegislacaoLista(
carregandoLegislacao: legislacaoProvider.carregandoLegislacao,
legislacoes: legislacaoProvider.legislacoes,
reseting: legislacaoProvider.reseting,
carregarDados: carregarDados,
isFiltroEmpty: legislacaoProvider.isFiltroEmpty,
);
}
#override
Widget build(BuildContext context) {
super.build(context);
final legislacaoProvider = Provider.of<LegislacaoProvider>(context);
return Scaffold(
appBar: CustomAppBar(
title: 'Legislação',
actions: <Widget>[
IconButton(
icon: Icon(
Icons.search,
color: legislacaoProvider.isFiltroEmpty
? Colors.white
: CustomColors.verde2,
),
onPressed: () {
Navigator.of(context)
.pushNamed(PesquisarLegislacaoScreen.routeName);
},
),
],
),
backgroundColor: Colors.white,
body: renderBody(legislacaoProvider),
);
}
Provider:
class LegislacaoProvider with ChangeNotifier {
bool _carregandoLegislacao = true;
bool _erroCarregandoLegislacao = false;
List<Legislacao> legislacoes = [];
int currentPage = 0;
bool _reseting = false;
LegislacaoApi _legislacaoApi;
LegislacaoProvider({LegislacaoApi legislacaoApi})
: _legislacaoApi = legislacaoApi ?? LegislacaoApiService();
bool get carregandoLegislacao {
return _carregandoLegislacao;
}
bool get erroCarregandoLegislacao {
return _erroCarregandoLegislacao;
}
bool get reseting {
return _reseting;
}
Future<void> carregarLegislacao({
int page = 1,
bool reset = false,
}) async {
try {
_carregandoLegislacao = true;
_erroCarregandoLegislacao = false;
_reseting = reset;
if (reset) {
page = 1;
}
notifyListeners();
legislacoes = await _legislacaoApi.getLegislacoes(
page: page,
ementa: filtro['ementa'],
conteudo: filtro['conteudo'],
ano: filtro['ano'],
periodoInicialLegislacao: filtro['periodoInicialLegislacao'],
periodoFinalLegislacao: filtro['periodoFinalLegislacao'],
tipoLegislacao: filtro['tipoLegislacao']?.id,
numero: filtro['numero'],
autor: filtro['autor'],
);
_carregandoLegislacao = false;
_reseting = false;
notifyListeners();
} catch (err) {
print(err);
_erroCarregandoLegislacao = true;
_carregandoLegislacao = false;
_reseting = false;
notifyListeners();
throw TaNaLeiException(err.toString());
}
}
}
MockApi:
class LegislacaoApiServiceMock extends LegislacaoApi {
bool _fail = false;
LegislacaoApiServiceMock();
LegislacaoApiServiceMock.fail() : _fail = true;
#override
Future<List<Legislacao>> getLegislacoes({
int page = 1,
String conteudo,
String ementa,
String ano,
DateTime periodoInicialLegislacao,
DateTime periodoFinalLegislacao,
int tipoLegislacao,
String numero,
String autor,
}) async {
if (_fail) {
throw Error();
}
final file = File('test/data/get_legislacoes.json');
print('step 1');
final json = await file.readAsString();
print('step 2 '); // <-- NEVER GETS PRINTED
return jsonDecode(json)
.map<Legislacao>(
(elemento) => Legislacao.fromJson(elemento),
)
.toList();
}
}
And finally, my tests:
final locator = GetIt.instance;
void setupLocatorLegislacaoProvider({LegislacaoApi legislacaoApi}) {
locator.registerLazySingleton<LegislacaoProvider>(() => LegislacaoProvider(
legislacaoApi: legislacaoApi,
));
}
void main() async {
TestWidgetsFlutterBinding.ensureInitialized();
setupLocatorLegislacaoProvider(legislacaoApi: LegislacaoApiServiceMock());
group('LegislacaoScreen', () {
Widget buildWidget() {
return ChangeNotifierProvider.value(
value: locator<LegislacaoProvider>();,
child: MaterialApp(
home: LegislacaoScreen(),
routes: routes,
),
);
}
testWidgets('builds screen', (WidgetTester tester) async {
final child = buildWidget();
await tester.pumpWidget(child);
expect(find.byWidget(child), findsOneWidget);
});
testWidgets('finds list when data is loaded',
(WidgetTester tester) async {
await tester.pumpWidget(buildWidget());
await tester.pump();
await tester.pump();
expect(find.byType(LegislacaoLista), findsOneWidget);
});
});
}
EDIT:
Here is the error message from running the tests:
➜ ta_na_lei git:(testes) ✗ flutter test test/ui/screens/legislacao/legislacao_screen_test.dart
00:03 +0: LegislacaoScreen builds screen
dentro de mock 1
00:04 +1: LegislacaoScreen exibe circular progress indicator quando carregando legislacao e reset true
dentro de mock 1
00:04 +2: LegislacaoScreen exibe lista de legislacao quando legislacoes carregadas
dentro de mock 1
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following TestFailure object was thrown running a test:
Expected: exactly one matching node in the widget tree
Actual: _WidgetTypeFinder:<zero widgets with type "LegislacaoLista" (ignoring offstage widgets)>
Which: means none were found but one was expected
When the exception was thrown, this was the stack:
#4 main.<anonymous closure>.<anonymous closure> (file:///Users/home/Projetos/casacivil/ta_na_lei/test/ui/screens/legislacao/legislacao_screen_test.dart:49:7)
<asynchronous suspension>
#5 main.<anonymous closure>.<anonymous closure> (file:///Users/home/Projetos/casacivil/ta_na_lei/test/ui/screens/legislacao/legislacao_screen_test.dart)
#6 testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:140:29)
<asynchronous suspension>
#7 testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart)
#8 TestWidgetsFlutterBinding._runTestBody (package:flutter_test/src/binding.dart:703:19)
<asynchronous suspension>
#11 TestWidgetsFlutterBinding._runTest (package:flutter_test/src/binding.dart:683:14)
#12 AutomatedTestWidgetsFlutterBinding.runTest.<anonymous closure> (package:flutter_test/src/binding.dart:1083:24)
#18 AutomatedTestWidgetsFlutterBinding.runTest (package:flutter_test/src/binding.dart:1080:15)
#19 testWidgets.<anonymous closure> (package:flutter_test/src/widget_tester.dart:133:24)
#20 Declarer.test.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:172:27)
<asynchronous suspension>
#21 Declarer.test.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart)
#22 Invoker.waitForOutstandingCallbacks.<anonymous closure> (package:test_api/src/backend/invoker.dart:246:15)
#27 Invoker.waitForOutstandingCallbacks (package:test_api/src/backend/invoker.dart:243:5)
#28 Declarer.test.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:170:33)
#33 Declarer.test.<anonymous closure> (package:test_api/src/backend/declarer.dart:169:13)
#34 Invoker._onRun.<anonymous closure>.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/invoker.dart:400:30)
(elided 31 frames from class _FakeAsync, class _RawReceivePortImpl, class _Timer, dart:async, dart:async-patch, and package:stack_trace)
This was caught by the test expectation on the following line:
file:///Users/home/Projetos/casacivil/ta_na_lei/test/ui/screens/legislacao/legislacao_screen_test.dart line 49
The test description was:
exibe lista de legislacao quando legislacoes carregadas
════════════════════════════════════════════════════════════════════════════════════════════════════
00:04 +2 -1: LegislacaoScreen exibe lista de legislacao quando legislacoes carregadas [E]
Test failed. See exception logs above.
The test description was: exibe lista de legislacao quando legislacoes carregadas
00:04 +3 -1: Some tests failed.
EDIT 2:
It seems the issue is with the async environment, after I read this article https://medium.com/flutter/event-loop-in-widget-tester-50b3ca5e9fc5 . I tried to call my test inside a runAsync method, it did not work, then I added await Future.delayed(Duration(seconds: 5)) and It worked. For some reason its taking a long time to read the file (In other tests it reads really fast). One interesting thing is that pump with a duration does not delay the tests...
Well, it works now with this workaround, but I'd like to know the correct way to fix the issue.
await tester.runAsync(() async {
await tester.pumpWidget(buildWidget());
await Future.delayed(Duration(seconds: 5));
await tester.pump(Duration(seconds: 2));
expect(find.byType(LegislacaoLista), findsOneWidget);
});