Flutter Test for API Helper class using Dio - flutter

Question

I am using a helper class to make request to server for that I am using Dio.
I want to test the helper class
this is my helper class
import 'package:dio/dio.dart';
import '../error/exceptions.dart';
enum HttpMethod { GET, POST, PUT, DELETE }
abstract class ApiClient {
Future<Response> request(
HttpMethod method,
String path, {
Map<String, dynamic>? headers,
Map<String, dynamic>? queryParams,
dynamic body,
});
}
/// This class provides http calls using dio package
class ApiClientImpl implements ApiClient {
final Dio dio;
ApiClientImpl({required this.dio});
#override
Future<Response> request(
HttpMethod method,
String path, {
Map<String, dynamic>? headers,
Map<String, dynamic>? queryParams,
dynamic body,
}) async {
// we can add headers here which are common for every restapi call
// headers = {'content-type': 'application/json'};
try {
final _response = await dio.request(
path,
options: Options(
method: _getApiMethodString(method),
headers: headers,
),
queryParameters: queryParams,
data: body,
);
return _response;
} on DioError {
throw FetchDataException('Dio Error Occurred');
}
}
String _getApiMethodString(HttpMethod method) {
switch (method) {
case HttpMethod.GET:
return 'GET';
case HttpMethod.POST:
return 'POST';
case HttpMethod.PUT:
return 'PUT';
case HttpMethod.DELETE:
return 'DELETE';
}
}
}
The test I wrote for it is
#GenerateMocks([Dio])
void main() {
late MockDio dio;
late ApiClientImpl apiClient;
setUp(() {
dio = MockDio();
apiClient = ApiClientImpl(dio: dio);
});
group('ApiService class methods test', () {
test('Should return response when request to server is made', () async {
// arrange
var successMessage = {'message': 'Success'};
const baseUrl = 'https://example.com/';
final options = Options(method: 'GET', headers: null);
when(dio.request(baseUrl,
options: options, queryParameters: anyNamed('queryParameters')))
.thenAnswer((_) async => Response(
requestOptions: RequestOptions(path: baseUrl),
data: successMessage,
statusCode: 200));
// act
final response = await apiClient.request(HttpMethod.GET, baseUrl);
// assert
expect(response.data, successMessage);
});
});
}
I am getting an error
MissingStubError: 'request'
No stub was found which matches the arguments of this method call:
request('https://example.com/', {data: null, queryParameters: null, cancelToken: null, options: Instance of 'Options', onSendProgress: null, onReceiveProgress: null})
How Can I write a correct test for the helper class.