Image class

main.dart

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Image.network('[Place an image link here!]'),
      ],
    );
  }
}

test.dart

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Directionality(
      textDirection: TextDirection.ltr,
      child: Container(
        color: Color(0xffeeeeee),
        child: Center(
          child: Container(
            child: MyWidget(),
            color: Color(0xffcccccc),
          ),
        ),
      ),
    );
  }
}

Future<void> main() async {
  final completer = Completer<void>();
  
  runApp(MyApp());

  WidgetsFlutterBinding.ensureInitialized()
      .addPostFrameCallback((timestamp) async {
    completer.complete();
  });
  
  await completer.future;

  final controller = LiveWidgetController(WidgetsBinding.instance);

  final rows = controller.widgetList(find.byType(Row));

  if (rows.length == 0) {
    _result(false, ['Couldn\'t find a Row!']);
    return;
  }

  if (rows.length > 1) {
    _result(false, ['Found ${rows.length} Rows, rather than just one.']);
    return;
  }

  final row = rows.first as Row;

  if (row.mainAxisSize != MainAxisSize.max) {
    _result(false, ['It\'s best to leave the mainAxisSize set to MainAxisSize.max, so there\'s space for the alignments to take effect.']);
    return;
  }
 
}