How to unit test a class that is created by provider?

Question

So let's say I have a Counter class like this

class Counter extends ChangeNotifier {
  int _i = 0;

  int get myCounter => _i;
  
  void increment() {
    _i++;
    notifyListeners();
  }

  void decrement() {
    _i--;
    notifyListeners();
  }
}

I want to write a test file for it, so I expose its instance like this. The problem is, after I expose it, how do I access the instance of the class I just created? Like say, I increased _i value through a button, how will I access the instance that is created by Provider in order to test it?

Answer 1

I was looking to do the same but then I found this answer https://stackoverflow.com/a/67704136/8111212

Basically, you can get the context from a widget, then you can use the context to get the provider state

Btw, you should test a public variable like i instead of _i

Code sample:

testWidgets('showDialog', (WidgetTester tester) async {
  await tester.pumpWidget(MaterialApp(home: Material(child: Container())));
  final BuildContext context = tester.element(find.byType(Scaffold)); // It could  be  final BuildContext context = tester.element(find.byType(Container)) depending on your app

  final Counter provider = Provider.of<Counter>(context, listen: false);
  expect(provider.i, equals(3));
});