Replaces system viewconfiguration

fake_view_configuration.dart

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class CustomWidgetsFlutterBinding extends WidgetsFlutterBinding {
  @override
  ViewConfiguration createViewConfiguration() {
    final ratio = 4.0;
    return ViewConfiguration(
      size: window.physicalSize / ratio,
      devicePixelRatio: ratio,
    );
  }

  static WidgetsBinding ensureInitialized() {
    if (WidgetsBinding.instance == null) {
      CustomWidgetsFlutterBinding();
    }
    return WidgetsBinding.instance;
  }
}

void main() {
  CustomWidgetsFlutterBinding.ensureInitialized()
    ..attachRootWidget(
      Center(
        child: Container(width: 50, height: 50, color: Colors.red),
      ),
    )
    ..scheduleWarmUpFrame();
}