Problems at Flutter/Dart Unit Test development - flutter

Question

I'm trying to code the Unit Test for my DataSourceImpl class, but I'm facing a problem with the methods that are called into the testing method.
I mocked and set the return for all methods into the DataSource testing method with the when statement, but it's not working...
Into the save and remove methods the Stream is called to notify the changes.
I'm using mocktail: ^0.1.4 for mocking dependency objects.
DATASOURCE IMPLEMENTATION
class DocumentDataSourceImpl implements IDocumentDataSource {
final FlutterSecureStorage _storage;
final StreamController<List<DocumentModel>> _streamController;
DocumentDataSourceImpl(this._storage, this._streamController);
#override
Future<void> remove(String id) async {
try {
await _storage.delete(key: id);
_streamController.sink.add(await getAll());
} catch (e) {
throw DocumentNotRemovedException();
}
}
#override
Future<void> save(DocumentModel model) async {
try {
await _storage.write(key: model.id, value: json.encode(model.toJson()));
_streamController.sink.add(await getAll());
} catch (e) {
throw DocumentNotSavedException();
}
}
#override
Future<List<DocumentModel>> getAll() async {
final result = await _storage.readAll();
return result.entries
.map((e) => DocumentModel.fromJson(json.decode(e.value)))
.toList();
}
}
UNIT TEST
void main() {
// Global Definitions
//-----Main Objects
late FlutterSecureStorageMock storage;
late StreamControllerMock<List<DocumentModel>> streamController;
late DocumentDataSourceImpl dataSource;
// SetUp Test
setUp(() {
//-----Objects Initialization
storage = FlutterSecureStorageMock();
streamController = StreamControllerMock();
dataSource = DocumentDataSourceImpl(storage, streamController);
});
group(("DocumentDataSource: Remove"), () {
final tArgument = "Document 1";
test("[P] Should remove the DocumentModel on Storage", () async {
//-----Arrange
when(() => storage.readAll())
.thenAnswer((_) async => tDocumentModelListMap);
when(() => dataSource.getAll())
.thenAnswer((_) async => tDocumentModelList);
when(() => streamController.sink.add(tDocumentModelList));
when(() => storage.delete(key: tArgument)).thenAnswer((_) async => null);
//-----Act
dataSource.remove(tArgument);
//-----Assert
verify(() => storage.delete(key: tArgument)).called(1);
verify(() => streamController.sink.add(tDocumentModelList)).called(1);
});
test(
"[N] Should return a DocumentNotRemovedException when the call of Storage is unsuccessful.",
() async {
//-----Arrange
when(() => storage.delete(key: tArgument)).thenThrow(
GenericExceptionMock(),
);
//-----Act
final result = dataSource.remove(tArgument);
//-----Assert
expect(result, throwsA(DocumentNotRemovedException()));
verify(() => storage.delete(key: tArgument)).called(1);
verifyNever(() => streamController.sink.add(tDocumentModelList));
});
});
group(("DocumentDataSource: Save"), () {
final tArgument = tDocumentModel;
test("[P] Should save the DocumentModel on Storage", () async {
//-----Arrange
when(() => storage.readAll())
.thenAnswer((_) async => tDocumentModelListMap);
when(() => dataSource.getAll())
.thenAnswer((_) async => tDocumentModelList);
when(() => streamController.sink.add(tDocumentModelList));
when(() => storage.write(
key: tArgument.id, value: json.encode(tArgument.toJson())));
//-----Act
dataSource.save(tArgument);
//-----Assert
verify(() => storage.write(
key: tArgument.id, value: json.encode(tArgument.toJson()))).called(1);
// verify(() => realTimeEvents.update(tDocumentModelList)).called(1);
});
test(
"[N] Should return a DocumentNotSavedException when the call of Storage is unsuccessful.",
() async {
//-----Arrange
when(() => storage.write(
key: tArgument.id, value: json.encode(tArgument.toJson()))).thenThrow(
GenericExceptionMock(),
);
//-----Act
final result = dataSource.save(tArgument);
//-----Assert
expect(result, throwsA(DocumentNotSavedException()));
verify(() => storage.write(
key: tArgument.id, value: json.encode(tArgument.toJson()))).called(1);
verifyNever(() => streamController.sink.add(tDocumentModelList));
});
});
}
MOCKS
class FlutterSecureStorageMock extends Mock implements FlutterSecureStorage {}
class StreamControllerMock<T> extends Mock implements StreamController<T> {}
ERROR LOG
type 'Null' is not a subtype of type 'Future<Map<String, String>>'
FlutterSecureStorageMock.readAll
DocumentDataSourceImpl.getAll
main.<fn>.<fn>.<fn>
when.<fn>
main.<fn>.<fn>
main.<fn>.<fn>
===== asynchronous gap ===========================
dart:async _completeOnAsyncError
package:memo/features/data/datasources/document_datasource_impl.dart DocumentDataSourceImpl.getAll
main.<fn>.<fn>.<fn>
when.<fn>
main.<fn>.<fn>
main.<fn>.<fn>
Bad state: Cannot call `when` within a stub response
when
main.<fn>.<fn>
main.<fn>.<fn>
✖ DocumentDataSource: Remove [P] Should remove the DocumentModel on Storage
Bad state: Cannot call `when` within a stub response
when
main.<fn>.<fn>
main.<fn>.<fn>
✖ DocumentDataSource: Remove [N] Should return a DocumentNotRemovedException when the call of Storage is unsuccessful.
Bad state: Cannot call `when` within a stub response
when
main.<fn>.<fn>
main.<fn>.<fn>
✖ DocumentDataSource: Save [P] Should save the DocumentModel on Storage
Bad state: Cannot call `when` within a stub response
when
main.<fn>.<fn>
main.<fn>.<fn>
✖ DocumentDataSource: Save [N] Should return a DocumentNotSavedException when the call of Storage is unsuccessful.
Exited (1)