Flutter测试报错：No GoRouter found in context，如何Mock上下文？

你在测试调用context.goNamed的ViewModel时，因为Mock的BuildContext中没有GoRouter实例，导致报错"No GoRouter found in context"。这是因为goNamed是GoRouter的扩展方法，并非BuildContext本身的方法，直接Mock BuildContext的goNamed无效。以下是两种可行的解决方案：

方案一：Mock GoRouter并关联到上下文 #

无需修改现有ViewModel代码，通过Mock GoRouter并让GoRouter.of(context)返回这个Mock实例来解决：

1. 创建MockGoRouter类：

import 'package:go_router/go_router.dart';
import 'package:mockito/mockito.dart';

class MockGoRouter extends Mock implements GoRouter {}

2. 修改测试代码：

void main() {
  group("MainScreenViewModel Tests", () {
    late MainScreenViewModel viewModel;
    late MockGoRouter mockRouter;

    setUp(() {
      viewModel = MainScreenViewModel();
      mockRouter = MockGoRouter();
      // 让GoRouter.of(context)返回Mock实例
      when(() => GoRouter.of(any())).thenReturn(mockRouter);
    });

    test("MoveToTab should change currentIndex and trigger navigation", () {
      final context = MockBuildContext();
      int notifyCount = 0;
      // 监听notifyListeners调用次数
      viewModel.addListener(() => notifyCount++);

      viewModel.moveToTab(context, index: 1);

      expect(viewModel.currentIndex, 1);
      // 验证路由跳转方法被正确调用
      verify(() => mockRouter.goNamed("/b")).called(1);
      // 验证notifyListeners被触发
      expect(notifyCount, 1);
    });
  });
}

方案二：重构ViewModel，依赖注入GoRouter（推荐） #

将GoRouter从上下文抽离，通过构造函数注入到ViewModel中，解耦ViewModel与BuildContext，测试逻辑更简洁：

1. 修改ViewModel代码：

import 'package:go_router/go_router.dart';
import 'package:flutter/foundation.dart';

const List<String> routeList = ["/a", "/b"];

class MainScreenViewModel extends ChangeNotifier {
  final GoRouter _router;
  int _currentIndex = 0;

  int get currentIndex => _currentIndex;

  // 构造函数注入GoRouter
  MainScreenViewModel(this._router);

  void moveToTab({required int index}) {
    _currentIndex = index;
    _router.goNamed(routeList[index]);
    notifyListeners();
  }
}

2. 对应的测试代码：

import 'package:mockito/mockito.dart';
import 'package:go_router/go_router.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group("MainScreenViewModel Tests", () {
    late MainScreenViewModel viewModel;
    late MockGoRouter mockRouter;

    setUp(() {
      mockRouter = MockGoRouter();
      viewModel = MainScreenViewModel(mockRouter);
    });

    test("MoveToTab should change currentIndex and trigger navigation", () {
      int notifyCount = 0;
      viewModel.addListener(() => notifyCount++);

      viewModel.moveToTab(index: 1);

      expect(viewModel.currentIndex, 1);
      verify(() => mockRouter.goNamed("/b")).called(1);
      expect(notifyCount, 1);
    });
  });
}

class MockGoRouter extends Mock implements GoRouter {}

方案对比 #

• 方案一：无需修改现有业务代码，适合快速修复测试问题，但仍保留了ViewModel对BuildContext的依赖。
• 方案二：通过依赖注入解耦，符合单一职责原则，测试逻辑更清晰，是更优的架构选择。

内容的提问来源于stack exchange，提问作者maxmitz