mocking Dio is not working to test my app in Flutter - flutter

Question

I am trying to write unit tests for my request with Dio but I keep getting this error:
type 'Null' is not a subtype of type 'BaseOptions'
I tried adding the base options on DioMock in a lot of different ways but the test remains the same.
How can I fix it?
Bellow are my Network class and the test class.
class NetworkService {
final Dio dio;
NetworkService(this.dio){
dio.options.baseUrl = "https://food2fork.ca/api/recipe/search";
dio.options.headers['Authorization'] = 'Token 9c8b06d329136da358c2d00e76946b0111ce2c48';
dio.interceptors.add(InterceptorsWrapper(
onRequest: (options, handler){
print('base ${options.baseUrl}');
print("PATH: ${options.path}");
return handler.next(options);
},
onResponse: (response, handler){
print("RESPONSE: ${response.statusCode} PATH: ${response.requestOptions.path}");
return handler.next(response);
},
onError: (DioError e, handler){
print("ERROR: ${e.response?.statusCode} => PATH: ${e.requestOptions.path}");
return handler.next(e);
}
));
}
Future<List<Recipe>> getRecipe() async {
var response = await dio.get('/?page=1&query=beef');
print("response ${response.data}");
if(response.statusCode == 200){
final List<Recipe> recipeList = [];
for(Map<String, dynamic> recipe in response.data['results']){
recipeList.add(Recipe.fromJson(recipe));
}
return recipeList;
} else {
throw Exception('sss');
}
// ONBOARDING
}
}
class DioMock extends Mock implements DioForNative {}
class RecipeMock extends Mock implements Recipe {}
main() {
final dio = DioMock();
final service = NetworkService(dio);
dio.options.baseUrl = "https://food2fork.ca/api/recipe/search";
dio.options.headers = { 'Content-type': 'application/json', 'Accept': 'application/json' };
test("should return Onboarding Model", () async {
final response = Response(
requestOptions: RequestOptions(
path: 'gfh',
baseUrl: "fgh"
),
data: RecipeMock()
);
when(dio.get(
"https://food2fork.ca/api/recipe/search"))
.thenAnswer((_) async => response);
final result = await service.getRecipe();
expect(result, isA<Recipe>());
});
}

Answer 1

You should use https://pub.dev/packages/http_mock_adapter package to help you mock your DIO requests
See its example https://github.com/lomsa-dev/http-mock-adapter/blob/main/example/main.dart :
void main() async {
late Dio dio;
late DioAdapter dioAdapter;
Response<dynamic> response;
group('Accounts', () {
const baseUrl = 'https://example.com';
const userCredentials = <String, dynamic>{
'email': 'test#example.com',
'password': 'password',
};
setUp(() {
dio = Dio(BaseOptions(baseUrl: baseUrl));
dioAdapter = DioAdapter(dio: dio);
});
test('signs up user', () async {
const route = '/signup';
dioAdapter.onPost(
route,
(server) => server.reply(201, null),
data: userCredentials,
);
// Returns a response with 201 Created success status response code.
response = await dio.post(route, data: userCredentials);
expect(response.statusCode, 201);
});
...
final dioError = DioError(
error: {'message': 'Some beautiful error!'},
requestOptions: RequestOptions(path: path),
response: Response(
statusCode: 500,
requestOptions: RequestOptions(path: path),
),
type: DioErrorType.response,
);
test("should return a DioError", () async {
dioAdapter.onGet(
path,
(server) {
server.throws(404, dioError );
});
final result = await service.getOnboardingAnswer("lastAnswerId");
expect(result, throwsA(isA<DioError>()));
});
}
});