如何基于Stacked Architecture进行Widget测试？

问题场景 #

采用Stacked架构+控制反转的Flutter项目中，单元测试运行正常，但执行Widget/集成测试时启动阶段报错，提示AuthService或NavigationService未在GetIt中注册。

测试代码示例：

import 'package:flutter_test/flutter_test.dart';
import 'package:my_project/ui/start_up/startup_viewmodel.dart';

void main() {
  testWidgets(
    "Simple widget test",
    (WidgetTester tester) async {
      await tester.pumpWidget(StartUpView());
    },
  );
}

报错信息：

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building StartUpView:
Object/factory with  type AuthService is not registered inside GetIt.
(Did you accidentally do GetIt sl=GetIt.instance(); instead of GetIt sl=GetIt.instance;
Did you forget to register it?)
'package:get_it/get_it_impl.dart':
Failed assertion: line 372 pos 7: 'instanceFactory != null'

The relevant error-causing widget was:
  StartUpView
  StartUpView:file:path/my_project/lib/app/app.router.dart:87:37

问题根源：StartUpView对应的ViewModel通过locator<T>获取服务，但测试环境未初始化Stacked的依赖注入容器，也未注册所需服务。

解决方法 #

1. 手动初始化Locator并注册依赖 #

在测试用例执行前，初始化Stacked的locator并注册所有ViewModel依赖的服务，推荐使用Mock类隔离测试逻辑：

import 'package:flutter_test/flutter_test.dart';
import 'package:my_project/ui/start_up/startup_view.dart';
import 'package:my_project/services/auth_service.dart';
import 'package:my_project/services/navigation_service.dart';
import 'package:stacked/stacked.dart';
import 'package:mockito/mockito.dart';

// 生成Mock服务类（需依赖mockito包）
class MockAuthService extends Mock implements AuthService {}
class MockNavigationService extends Mock implements NavigationService {}

void main() {
  setUp(() {
    // 重置locator，确保每个测试用例环境干净
    locator.reset();
    // 注册Mock服务
    locator.registerLazySingleton<AuthService>(() => MockAuthService());
    locator.registerLazySingleton<NavigationService>(() => MockNavigationService());
  });

  testWidgets("Simple widget test", (WidgetTester tester) async {
    await tester.pumpWidget(const StartUpView());
    // 可添加断言验证页面状态，例如：
    // expect(find.text("Welcome"), findsOneWidget);
  });
}

2. 使用StackedTest包简化测试流程 #

Stacked官方提供stacked_test包，可自动处理locator的初始化与清理，简化测试代码：

import 'package:flutter_test/flutter_test.dart';
import 'package:my_project/ui/start_up/startup_view.dart';
import 'package:my_project/services/auth_service.dart';
import 'package:my_project/services/navigation_service.dart';
import 'package:stacked_test/stacked_test.dart';
import 'package:mockito/mockito.dart';

class MockAuthService extends Mock implements AuthService {}
class MockNavigationService extends Mock implements NavigationService {}

void main() {
  testWidgets("Simple widget test", (WidgetTester tester) async {
    // 一键初始化测试环境并注册依赖
    await setupTestWidget(
      tester: tester,
      widget: const StartUpView(),
      dependencies: [
        LazySingletonMock<AuthService>(MockAuthService()),
        LazySingletonMock<NavigationService>(MockNavigationService()),
      ],
    );

    // 执行测试断言
    expect(find.byType(StartUpView), findsOneWidget);
  });
}

3. 集成测试适配 #

集成测试的处理逻辑与Widget测试一致，只需在测试入口处初始化locator并注册所有必要依赖，再启动App：

import 'package:flutter_test/flutter_test.dart';
import 'package:integration_test/integration_test.dart';
import 'package:my_project/main.dart';
import 'package:my_project/services/auth_service.dart';
import 'package:my_project/services/navigation_service.dart';
import 'package:stacked/stacked.dart';
import 'package:mockito/mockito.dart';

class MockAuthService extends Mock implements AuthService {}
class MockNavigationService extends Mock implements NavigationService {}

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  setUp(() {
    locator.reset();
    locator.registerLazySingleton<AuthService>(() => MockAuthService());
    locator.registerLazySingleton<NavigationService>(() => MockNavigationService());
  });

  testWidgets("Integration test example", (WidgetTester tester) async {
    await tester.pumpWidget(const MyApp());
    // 执行集成测试逻辑
  });
}

内容的提问来源于stack exchange，提问作者Jakub F. Romański