Flutter mocktail get error when put mock getx controller - flutter

Question

I have this getx controller :
class CustomerPOAutocompleteState extends GetxController {
CustomerPOAutocompleteState();
...
Future<void> getCustomer(String title, String? propertyId) async {
var result = await RRGraphQL().artemis!...
_customers =...
update(['update']);
}
Now by Mock mocktail I created a mock class:
class MockController extends Mock implements CustomerPOAutocompleteState {}
When I try to put it I got error:
void main() {
late MockController mockController;
setUpAll(() {
mockController = MockController();
});
...
testWidgets('test', (WidgetTester tester) async {
Get.put<CustomerPOAutocompleteState>(mockController,tag: "");
error:
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following _TypeError was thrown running a test:
type 'Null' is not a subtype of type 'InternalFinalCallback<void>'

Answer 1

UPDATED Answer
This error occurs since Get.put performs calls on your GetxController which have not been mocked out correctly.
You can either do this manually (you will have to check the implementation details of Get.put and GetxController). Or you can do, what the Get documentation suggests and let your mock extend GetxController and use Mock as a mixin.
class MockController extends GetxController
with Mock
implements CustomerPOAutocompleteState {}
Check out this full example:
import 'package:flutter_test/flutter_test.dart';
import 'package:get/get.dart';
import 'package:mocktail/mocktail.dart';
class DemoController extends GetxController {
var count = 0.obs;
increment() => count++;
}
class MockController extends GetxController
with Mock
implements DemoController {}
main() {
late MockController mockController;
setUpAll(() {
mockController = MockController();
});
test('GetX Test', () {
when(() => mockController.count).thenAnswer((_) => 12.obs);
Get.put<DemoController>(mockController, tag: "");
mockController.increment();
expect(mockController.count.value, 12);
});
}