How to locate multiple widget of same type in widget hierarchy?

I am developing some intregration tests for one of my flutter-web application. I wanted to specifically locate the container(width: 50, height: 50) in the following below widget hierarchy tree considering top to bottom approach. ParentWidget --> Row --> Text, SizedBox, Row --> Container(), Container(width: 50, height: 50), Container(). Note: Without key approach

I tried to locate using descendant of ParentWidget --> Row --> Row --> with index tried to select the 2nd container, but this isn't working, it fails with error "Bad state: No element".

import 'package:flutter/material.dart';

class ParentWidget extends StatelessWidget {
  const ParentWidget({Key? key});

  @override
  Widget build(BuildContext context) {
    return Row(
      crossAxisAlignment: CrossAxisAlignment.center,
      children: [
        Text("Hello World..!!"),
        SizedBox(
          width: 20,
        ),
        Row(
          crossAxisAlignment: CrossAxisAlignment.end,
          children: [
            Container(
              width: 20,
              height: 20,
              color: Colors.red,
            ),
            Container(
              width: 50,
              height: 50,
              color: Colors.red,
            ),
            Container(
              width: 20,
              height: 20,
              color: Colors.red,
            ),
          ],
        ),
      ],
    );
  }
}

final container = tester.widget<Container>(find.descendant(
    of: find.descendant(
        of: find.byType(ParentWidget), matching: find.byType(Row)),
    matching: find.descendant(
        of: find.byType(Row), matching: find.byType(Container).at(1))));

To find multiple widgets in a test you can do this:

testWidgets('Test containers', (tester) async {
    
    await tester.pumpWidget(ParentWidget());

    expect(find.byType(Container), findsNWidgets(3));
  });

For more info check https://docs.flutter.dev/cookbook/testing/widget/introduction

Edit: To test the second Container's width you could do something like this:

//get the second element's widget, index 1, cast it as a container and check its width
expect((find.byType(Container).evaluate().elementAt(1).widget as Container).constraints?.maxWidth, 50.0);