引数に応じた返り値の変更

mockito の when で返り値を制御する際に渡された引数に応じて返り値を変えたいとき

例えば以下のような場合に、FindProfileUseCase#execute から返される Profile を id に応じて変えたいとします。

class ProfileViewModel {
  ProfileViewModel({
    required FindProfileUseCase findProfileUseCase,
  }) : _findProfileUseCase = findProfileUseCase;

  final FindProfileUseCase _findProfileUseCase;

  Profile _profile = Profile.empty;

  int get id => _profile.id;

  void onIdChanged(int id) {
    _profile = _findProfileUseCase.execute(id: id);
  }
}

class Profile {
  const Profile({
    required this.id,
    required this.groupId,
    required this.name,
    required this.thumbnailUrl,
    required this.location,
  });

  ...
}

class FindProfileUseCase {
  Profile execute({required int id}) { ... }
}

Recipe

thenAnswer

thenAnswer を使用して realInvocation を見ることで引数を取得することができます。

test('test', () {
  when(findProfileUseCase.execute(id: anyNamed('id'))).thenAnswer(
    (realInvocation) => Profile(
      id: realInvocation.namedArguments[#id] as int,
      groupId: 0,
      name: 'name',
      thumbnailUrl: 'thumbnailUrl',
      location: 'location',
    ),
  );

  viewModel.onIdChanged(2);

  expect(viewModel.id, 2);
});

Result

@GenerateMocks([
  FindProfileUseCase,
])
void main() {
  late MockFindProfileUseCase findProfileUseCase;
  late ProfileViewModel viewModel;

  setUp(() {
    findProfileUseCase = MockFindProfileUseCase();
    viewModel = ProfileViewModel(
      findProfileUseCase: findProfileUseCase,
    );
  });

  test('test', () {
    when(findProfileUseCase.execute(id: anyNamed('id'))).thenAnswer(
      (realInvocation) => Profile(
        id: realInvocation.namedArguments[#id] as int,
        groupId: 0,
        name: 'name',
        thumbnailUrl: 'thumbnailUrl',
        location: 'location',
      ),
    );

    viewModel.onIdChanged(2);

    expect(viewModel.id, 2);
  });
}