我想用 mockito 插件测试我的提供者，但有一个问题，正如我对标题的理解。
当我执行打印（响应）时显示为空
如果我从 API 中删除标题
headers: {
'X-Requested-With': 'XMLHttpRequest',
'Authorization': 'Bearer $token',
},
测试工作正常，但带有标题：
NoSuchMethodError: The getter 'statusCode' was called on null.
Receiver: null
Tried calling: statusCode
dart:core Object.noSuchMethod
package:mba/resources/providers/post_provider.dart 38:20 PostProvider.fetchPosts
===== asynchronous gap ===========================
dart:async _AsyncAwaitCompleter.completeError
package:mba/resources/providers/post_provider.dart PostProvider.fetchPosts
===== asynchronous gap ===========================
dart:async _asyncThenWrapperHelper
package:mba/resources/providers/post_provider.dart PostProvider.fetchPosts
test/resources/providers/post_provider_test.dart 46:39 main.<fn>.<fn>
提供者：
import 'package:http/http.dart' as http;
import 'package:mba/env.dart';
import 'package:mba/core/models/post_model.dart';
class PostProvider {
final http.Client client;
final String _api = API;
// Map<String, List<Post>> _postsList …