Test fails due to generated mocks attemps to cast type 'Future<List<dynamic>>' to 'Future<Iterable<Weather>>'

[eriklange]

I'm mocking a method getWeather() which returns Future<Iterable<Weather>>()

It seems like the generated mock class' getWeather() creates a new Future<Iterable<dynamic>>, and then attempts to cast that directly to Future<Iterable<Weather>>, which does not work.

This results in the error

type 'Future<List<dynamic>>' is not a subtype of type 'Future<Iterable<Weather>>' in type cast
MockWeatherRepository.getWeather
test\…\weather\weather_bloc_test.mocks.dart:85
main.<fn>.<fn>.<fn>
test\…\weather\weather_bloc_test.dart:82
testBloc.<fn>
package:bloc_test/src/bloc_test.dart:160
testBloc.<fn>
package:bloc_test/src/bloc_test.dart:158
dart:async                                            runZonedGuarded
testBloc
package:bloc_test/src/bloc_test.dart:157
blocTest.<fn>
package:bloc_test/src/bloc_test.dart:129
blocTest.<fn>
package:bloc_test/src/bloc_test.dart:128
===== asynchronous gap ===========================
dart:async                                            _completeOnAsyncError
package:bloc_test/src/bloc_test.dart                  testBloc.<fn>
package:bloc_test/src/bloc_test.dart:1
testBloc.<fn>
package:bloc_test/src/bloc_test.dart:158
dart:async                                            runZonedGuarded

weather_bloc.test.dart:

@GenerateMocks([Weather, WeatherRepository])
main() {
  group('WeatherBloc', () {
    late WeatherRepository weatherRepository;
    late WeatherBloc weatherBloc;

    setUp(() {
      weatherRepository = MockWeatherRepository();
      weatherBloc = WeatherBloc(weatherRepository: weatherRepository);
    });

    tearDown(() {
      weatherBloc.close();
    });

    group('WeatherRefreshRequested', () {
      blocTest<WeatherBloc, WeatherState>(
        'Emits [WeatherLoadInProgress, WeatherLoadFailure] when weather repository throws error',
        build: () {
          when(weatherRepository.getWeather()).thenThrow('Weather Error');

          return weatherBloc;
        },
        act: (bloc) => bloc.add(WeatherRefreshRequested()),
        expect: () => [],
      );
    });
  });
}

MockWeatherRepository

class MockWeatherRepository extends _i1.Mock implements _i7.WeatherRepository {
  MockWeatherRepository() {
    _i1.throwOnMissingStub(this);
  }

  @override
  _i4.NasaApiClient get nasaApiClient =>
      (super.noSuchMethod(Invocation.getter(#nasaApiClient),
          returnValue: _FakeNasaApiClient()) as _i4.NasaApiClient);
  @override
  _i8.Future<Iterable<_i5.Weather>> getWeather() =>
      (super.noSuchMethod(Invocation.method(#getWeather, []),
          returnValue: Future.value([])) as _i8.Future<Iterable<_i5.Weather>>);
}

flutter doctor

$ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.0.4, on Microsoft Windows [Version 10.0.19041.867], locale en-GB)
[√] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[√] Chrome - develop for the web
[√] Android Studio (version 4.1.0)
[√] IntelliJ IDEA Community Edition (version 2017.1)
[√] VS Code (version 1.55.0)
[√] Connected device (2 available)

• No issues found!

I did manage to fix the problem by specifying the type in the object that is attempted to be casted to Future<Iterable>

MockWeatherRepository Fix

@override
  _i8.Future<Iterable<_i5.Weather>> getWeather() =>
      (super.noSuchMethod(Invocation.method(#getWeather, []),
          returnValue: Future<Iterable<Weather>>.value([])) as _i8.Future<Iterable<_i5.Weather>>);

The fix is that instead of Future.value([]), I specified the type as Future<Iterable<Weather>>.value([]))

Am I using mockito wrong, or is this a bug?

[srawlins]

Thanks for the bug report. At first glance,

It seems like the generated mock class' getWeather attempts to create a new Future<Iterable>, and then attempts to cast that directly to Future<Iterable>, which does not work.

Did GitHub eat some of your brackets and generics? Maybe use more backtick code snippets here?

[srawlins]

I think this is a valid bug though, I'll look into this ASAP.

[eriklange]

Thanks for the bug report. At first glance,

It seems like the generated mock class' getWeather attempts to create a new Future, and then attempts to cast that directly to Future, which does not work.

Did GitHub eat some of your brackets and generics? Maybe use more backtick code snippets here?

Yes it did, thanks! I edited the original comment now.