type 'Null' is not a subtype of type 'Future<bool>'

Question

I'm getting the below error while I'm trying to implement bloc testing in my flutter project

type 'Null' is not a subtype of type 'Future<bool>'
package:mynovatium/features/signup/repositories/signup_repository.dart 10:16  MockRepository.createAccountsignup

Following are the corresponding files that might help identify the cause of the error signup_bloc_test.dart

class MockRepository extends Mock implements SignUpRepository {}

void main() async {
  await configureInjection(inj.Environment.test);
  group('SignupBloc', () {
    late SignUpBloc signUpBloc;
    late SignUpRepository signupRepositoryMock;
    setUp(() {
      signupRepositoryMock = MockRepository();
      signUpBloc = SignUpBloc(signUpRepository: signupRepositoryMock);
    });

    test('initial state of the bloc is [AuthenticationInitial]', () {
      expect(SignUpBloc(signUpRepository: signupRepositoryMock).state,
          SignupInitial(),);
    });

    group('SignUpCreateAccount', () {
      blocTest<SignUpBloc, SignUpState>(
        'emits [SignUpCreateAccountLoading, SignupInitial] '
        'state when successfully Signed up',
        setUp: () {
          when(signupRepositoryMock.createAccount(
                'Nevil',
                'abcd',
                '[email protected]',
                'english',
              ),).thenAnswer((_) async  => Future<bool>.value(true));
        },
        build: () => SignUpBloc(signUpRepository: signupRepositoryMock),
        act: (SignUpBloc bloc) => bloc.add(
          const SignUpCreateAccount(
            'Nevil',
            'abcd',
            '[email protected]',
            'english',
          ),
        ),
        expect: () => [
          SignUpCreateAccountLoading(),
          SignupInitial(),
        ],
      );
    });
  });
}

signup_repository.dart This is the code for the signup repository.

class SignUpRepository {
  Future<bool> createAccount(String _firstName, String _lastName, String _eMailAddress, String _language) async {
    final Response _response;
    try {
      _response = await CEApiRequest().post(
        Endpoints.createCustomerAPI,
        jsonData: <String, dynamic>{
          'firstName': _firstName,
          'lastName': _lastName,
          'email': _eMailAddress,
          'language': _language,
          'responseUrl': Endpoints.flutterAddress,
        },
      );

      final Map<String, dynamic> _customerMap = jsonDecode(_response.body);
      final CustomerModel _clients = CustomerModel.fromJson(_customerMap['data']);

      if (_clients.id != null) {
        return true;
      } else {
        return false;
      }
    } on KBMException catch (e) {
      final KBMException _exception = e;
      throw _exception;
    }
  }
}

If anyone has any ideas on what might be the issue here, please help!!

Answer 1

Okay so in the above code you need to stub the methods within the mock repository as well and override it to have it return something incase null is being returned.

class MockRepository extends Mock implements SignUpRepository {
  @override
  Future<bool> createAccount(String? _firstName, String? _lastName, String? _eMailAddress, String? _language) =>
      super.noSuchMethod(Invocation.method(#createAccount, [_firstName, _lastName, _eMailAddress, _language]),
      returnValue:  Future<bool>.value(false),);
}

Doing something like that done in the above code works well.