纯Dart环境下Riverpod Stream Provider测试问题求助

第一个测试：Bad state: No element 错误 #

原因 #

你的AtFhirListen的build方法存在两个关键问题：

1. 调用atClient.notificationService.subscribe().map(...)后，没有将生成的流内容输出到Provider的流中，导致整个Provider的流是空的，调用stream.first自然会报错“无元素”。
2. 使用map处理流元素时，内部返回的是async*生成的子流，但map会把每个元素转换成Stream<AtFhirNotification>，而不是展开这些子流的元素。需要用asyncExpand替代map来展开子流。

修复后的Provider代码 #

@Riverpod(keepAlive: true)
class AtFhirListen extends _$AtFhirListen {
  @override
  Stream<AtFhirNotification> build(AtClient atClient) async* {
    // 使用yield* 将内部流的元素输出到Provider的流中
    // 使用asyncExpand 展开每个元素生成的子流
    yield* atClient.notificationService
        .subscribe(shouldDecrypt: true)
        .asyncExpand((AtNotification atNotification) async* {
      if (atNotification.value != null) {
        try {
          final AtFhirNotification atFhirNotification =
              AtFhirNotification.fromJsonString(atNotification.value!);
          yield atFhirNotification;
        } catch (exception) {
          // 可在此添加错误处理逻辑，比如记录日志或抛出错误
        }
      }
    });
  }
}

修复后的第一个测试代码 #

此时原测试代码即可正常运行，因为Provider的流现在会输出正确的元素：

class MockAtClient extends Mock implements AtClient {
  @override
  final NotificationService notificationService = MockNotificationService();
}

class MockNotificationService extends Mock implements NotificationService {
  @override
  Stream<AtNotification> subscribe({String? regex, bool? shouldDecrypt}) {
    return Stream<AtNotification>.fromIterable(<AtNotification>[
      AtNotification('id1', 'key1', '@from1', '@to1', 12345, 'text', true),
      AtNotification('id2', 'key2', '@from2', '@to2', 12345, 'text', true,
          value: Dstu2ResourceNotification(
                  dstu2.Patient(fhirId: dstu2.FhirId('id2')))
              .toJsonString()),
      AtNotification('id3', 'key3', '@from3', '@to3', 12345, 'text', true),
      AtNotification('id4', 'key4', '@from4', '@to4', 12345, 'text', true),
    ]);
  }
}

void main() {
  final MockAtClient atClient = MockAtClient();
  group('AtFhirListen', () {
    test('should return AtFhirNotification', () async {
      final Stream<AtFhirNotification> stream = AtFhirListen().build(atClient);
      expect(
          await stream.first,
          AtFhirNotification.dstu2Resource(
              dstu2.Patient(fhirId: dstu2.FhirId('id2'))));
    });
  });
}

第二个测试：Used on a non-mockito object 错误 #

原因 #

Mockito的verify方法只能作用于Mockito生成的Mock对象，你直接创建的Listener实例不是Mock对象，因此无法被verify校验。

修复方案 #

创建一个继承自Mock的MockListener类，用于监听Provider的状态变化：

修复后的第二个测试代码 #

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

// 定义MockListener类，实现Listener接口并继承Mock
class MockListener extends Mock implements Listener<AsyncValue<AtFhirNotification>> {}

class MockAtClient extends Mock implements AtClient {
  @override
  final NotificationService notificationService = MockNotificationService();
}

class MockNotificationService extends Mock implements NotificationService {
  @override
  Stream<AtNotification> subscribe({String? regex, bool? shouldDecrypt}) {
    return Stream<AtNotification>.fromIterable(<AtNotification>[
      AtNotification('id2', 'key2', '@from2', '@to2', 12345, 'text', true,
          value: Dstu2ResourceNotification(
                  dstu2.Patient(fhirId: dstu2.FhirId('id2')))
              .toJsonString()),
    ]);
  }
}

void main() {
  group('AtFhirListen', () {
    test('should notify listener with AtFhirNotification', () async {
      final MockAtClient atClient = MockAtClient();
      final ProviderContainer container = ProviderContainer();
      final MockListener listener = MockListener();

      container.listen(
        atFhirListenProvider(atClient),
        listener,
        fireImmediately: true,
      );

      // 等待流完成一次事件循环，确保Listener收到通知
      await Future<void>.delayed(Duration.zero);

      verify(
        () => listener(
          null,
          AsyncData<AtFhirNotification>(
            AtFhirNotification.dstu2Resource(
              dstu2.Patient(fhirId: dstu2.FhirId('id2')),
            ),
          ),
        ),
      ).called(1);
    });
  });
}

额外优化：规范Mockito使用方式 #

建议使用Mockito的when方法来Stub依赖方法，而不是直接重写Mock类的方法，这样可以更灵活地控制Mock行为，还能验证方法的调用情况：

void main() {
  late MockAtClient atClient;
  late MockNotificationService mockNotificationService;

  setUp(() {
    mockNotificationService = MockNotificationService();
    atClient = MockAtClient();
    // Stub notificationService属性
    when(() => atClient.notificationService).thenReturn(mockNotificationService);
    // Stub subscribe方法
    when(() => mockNotificationService.subscribe(shouldDecrypt: true)).thenAnswer((_) => Stream<AtNotification>.fromIterable([
          AtNotification('id2', 'key2', '@from2', '@to2', 12345, 'text', true,
              value: Dstu2ResourceNotification(
                      dstu2.Patient(fhirId: dstu2.FhirId('id2')))
                  .toJsonString()),
        ]));
  });

  group('AtFhirListen', () {
    test('should call subscribe with shouldDecrypt=true', () async {
      final Stream<AtFhirNotification> stream = AtFhirListen().build(atClient);
      await stream.first;
      // 验证subscribe方法是否被正确调用
      verify(() => mockNotificationService.subscribe(shouldDecrypt: true)).called(1);
    });
  });
}

内容的提问来源于stack exchange，提问作者Grey