Flutter: How to unit testing moor/drift? - flutter

Question

I already implementation of Drift for local storage, and want make it testable function. But I get stack and idk how to fix it the unit test.
HomeDao
#DriftAccessor(tables: [RepositoriesTable])
class HomeDao extends DatabaseAccessor<AppDatabase> with _$HomeDaoMixin {
HomeDao(AppDatabase db) : super(db);
Future<List<RepositoriesTableData>> getRepositories() async =>
await select(repositoriesTable).get();
}
AppDatabase
#DriftDatabase(
tables: [RepositoriesTable],
daos: [HomeDao],
)
class AppDatabase extends _$AppDatabase {
AppDatabase() : super(_openConnection());
#override
int get schemaVersion => 1;
}
QueryExecutor _openConnection() {
return SqfliteQueryExecutor.inDatabaseFolder(
path: 'db.sqlite',
logStatements: true,
);
}
LocalDataSources
abstract class GTHomeLocalDataSource {
const GTHomeLocalDataSource();
Future<List<RepositoriesTableData>> getRepositories();
}
class GTHomeLocalDataSourceImpl implements GTHomeLocalDataSource {
final AppDatabase appDatabase;
const GTHomeLocalDataSourceImpl({required this.appDatabase});
#override
Future<List<RepositoriesTableData>> getRepositories() async =>
await appDatabase.homeDao.getRepositories();
}
UnitTesting
void main() => testGTHomeLocalDataSource();
class MockDatabaseHandler extends Mock implements AppDatabase {}
void testGTHomeLocalDataSource() {
late GTHomeLocalDataSource localDataSource;
late AppDatabase databaseHandler;
setUp(() {
databaseHandler = MockDatabaseHandler();
localDataSource = GTHomeLocalDataSourceImpl(
appDatabase: databaseHandler,
);
});
group("GTHomeLocalDataSource -", () {
test(''' \t
GIVEN Nothing
WHEN call getRepositories
THEN databaseHandler select function has been called and return list of RepositoriesTableData
''', () async {
// GIVEN
when(() => databaseHandler.homeDao.getRepositories())
.thenAnswer((_) => Future.value(repositoriesDummyTable));
// WHEN
final result = await localDataSource.getRepositories();
// THEN
verify(() => databaseHandler.homeDao.getRepositories());
expect(result, isA<List<RepositoriesTableData>>());
expect(result.length, repositoriesDummyTable.length);
expect(result.first.language, repositoriesDummyTable.first.language);
});
});
tearDown(() async {
await databaseHandler.close();
});
}
My function is work well for get data from the local db and show it in the app, but when running as unit test, I stacked with this error.
package:gt_core/local/database/database_module.g.dart 424:22 MockDatabaseHandler.homeDao
package:gt_home/data/data_sources/gt_home_local_datasource.dart 20:25 GTHomeLocalDataSourceImpl.getRepositories
test/data/data_sources/gt_home_local_datasource_test.dart 35:44 testGTHomeLocalDataSource.<fn>.<fn>
test/data/data_sources/gt_home_local_datasource_test.dart 29:12 testGTHomeLocalDataSource.<fn>.<fn>
type 'Null' is not a subtype of type 'Future<void>'
package:drift/src/runtime/api/db_base.dart 125:16 MockDatabaseHandler.close
test/data/data_sources/gt_home_local_datasource_test.dart 47:27 testGTHomeLocalDataSource.<fn>
test/data/data_sources/gt_home_local_datasource_test.dart 46:12 testGTHomeLocalDataSource.<fn>
===== asynchronous gap ===========================
dart:async _completeOnAsyncError
test/data/data_sources/gt_home_local_datasource_test.dart testGTHomeLocalDataSource.<fn>
test/data/data_sources/gt_home_local_datasource_test.dart 46:12 testGTHomeLocalDataSource.<fn>
type 'Future<List<RepositoriesTableData>>' is not a subtype of type 'HomeDao'
Anyone know how to fix it?

Answer 1

If you use Mocking to test Drift database, then you'll need to mock the method call as well, otherwiser the method will return null which is the default behavior for Mockito. For example.
// return rowid
when(db.insertItem(any)).thenAnswer((_) => 1);
However it is recommended as per Drift documentation to use in-memory sqlite database which doesn't require real device or simulator for testing.
This issue was also has been discussed here
Using in memory database
import 'package:drift/native.dart';
import 'package:test/test.dart';
import 'package:my_app/src/database.dart';
void main() {
MyDatabase database;
MyRepo repo;
setUp(() {
database = MyDatabase(NativeDatabase.memory());
repo = MyRepo(appDatabase: database);
});
tearDown(() async {
await database.close();
});
group('mytest', () {
test('test create', () async {
await repo.create(MyDateCompanion(title: 'some name'));
final list = await repo.getItemList();
expect(list, isA<MyDataObject>())
})
});
}