// Copyright 2019 The Flutter Authors. All rights reserved.// Use of this source code is governed by a BSD-style license that can be// found in the LICENSE file.import'dart:ui'showwindow;import'package:flutter_test/flutter_test.dart';import'package:flutter/widgets.dart';voidmain(){test('Instantiating WidgetsFlutterBinding does neither schedule a frame nor register frame callbacks',()async{// Regression test for https://github.com/flutter/flutter/issues/39494.// Preconditions.expect(WidgetsBinding.instance,isNull);expect(window.onBeginFrame,isNull);expect(window.onDrawFrame,isNull);// Instantiation does nothing with regards to frame scheduling.finalWidgetsFlutterBindingbinding=WidgetsFlutterBinding.ensureInitialized();expect(binding.hasScheduledFrame,isFalse);expect(window.onBeginFrame,isNull);expect(window.onDrawFrame,isNull);// Frame callbacks are registered lazily when a frame is scheduled.binding.scheduleFrame();expect(window.onBeginFrame,isNotNull);expect(window.onDrawFrame,isNotNull);});}