颤振测试块错误类型'Null'不是类型的子类型答案

【问题标题】：Flutter test bloc error type 'Null' is not a subtype of type颤振测试块错误类型'Null'不是类型的子类型
【发布时间】：2021-10-08 05:53:55
【问题描述】：

我正在测试一个从 api 获取餐馆列表的 bloc 方法。

这是我的代码：

import 'package:bloc_test/bloc_test.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:mobile_app_engineer/blocs/merchant_bloc.dart';
import 'package:mobile_app_engineer/repositories/merchant_repository.dart';
import 'package:mockito/mockito.dart';
import 'package:mobile_app_engineer/models/list_merchants_response.dart';

class MockMerchantRepository extends Mock implements MerchantRepository {}

// Generate a MockClient using the Mockito package.
// Create new instances of this class in each test.
void main() {

late MockMerchantRepository mockMerchantRepository;

setUp((){
  mockMerchantRepository = MockMerchantRepository();
});

List<Merchant> merchantList = [
   Merchant object here    
];

blocTest<MerchantBloc, MerchantState>(
   'Check if merchant fetch return correct data',
   build: () {
   when(mockMerchantRepository.fetchMerchants(1)).thenThrow(NetworkError()); <=== in this line main 101
   return MerchantBloc(mockMerchantRepository);
},
  act: (bloc) => bloc.add(GetMerchantsList(1)),
  expect: () => [MerchantInitial(), GetMerchantsListState(merchantList)],
);

}

我收到此错误：

type 'Null' is not a subtype of type 'Future<List<Merchant>>'
package:mobile_app_engineer/repositories/merchant_repository.dart 14:26  
MockMerchantRepository.fetchMerchants
test/api_test/fetch_restaurant_test.dart 101:35                          main.<fn>
package:bloc_test/src/bloc_test.dart 176:25                              testBloc.<fn>

我做错了什么吗？谢谢

【问题讨论】：

有MerchantState和fetchMerchants()的详细代码

标签： flutter mockito flutter-test bloc-test

【解决方案1】：

找到解决方案：这是因为 null 安全性，所以现在我不得不添加 GenerateMocks 来为 api 调用生成一个模拟存储库。

import 'fetch_merchant_test.mocks.dart';

@GenerateMocks([MockMerchantRepository])
void main() {

final mockMerchantRepository = MockMockMerchantRepository();

【讨论】：