当您实现一个想要模拟的方法而不是让Mockito来模拟时，可能会发生这个问题。
下面的代码将返回Bad state: Mock method was not called within when(). Was a real method called?：

class MockFirebaseAuth extends Mock implements FirebaseAuth {
  FirebaseUser _currentUser;

  MockFirebaseAuth(this._currentUser);

  // This method causes the issue.
  Future<FirebaseUser> currentUser() async {
    return _currentUser;
  }
}

final user = MockFirebaseUser();
final mockFirebaseAuth = MockFirebaseAuth(user);

// Will throw `Bad state: Mock method was not called within `when()`. Was a real method called?`
when(mockFirebaseAuth.currentUser())
    .thenAnswer((_) => Future.value(user));

你想要的是：

class MockFirebaseAuth extends Mock implements FirebaseAuth {}

final user = MockFirebaseUser();
final mockFirebaseAuth = MockFirebaseAuth();

// Will work as expected
when(mockFirebaseAuth.currentUser())
    .thenAnswer((_) => Future.value(user));

当你尝试在一个非mock子类上调用when()时，也会发生这个问题：

class MyClass {
  String doSomething() {
    return 'test';
  }
}

final myClassInstance = MyClass();

// Will throw `Bad state: Mock method was not called within `when()`. Was a real method called?`
when(myClassInstance.doSomething())
    .thenReturn((_) => 'mockedValue');

还有一种可能性。如果你的模拟对象发生这种情况，那么它可能已经过时了。在这种情况下，尝试使用

flutter pub run build_runner build --delete-conflicting-outputs

请在拆卸或设置结束时声明resetMocktailState()，因此测试用例不应影响后续测试用例。

我找到的解决方案是在 test_driver/app.dart 中定义模拟，然后调用runApp函数，这样即使在flutter集成测试中也可以应用模拟：

import 'package:flutter/widgets.dart';
import 'package:flutter_driver/driver_extension.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:utgard/business/config/globals.dart';
import 'package:utgard/main.dart' as app;

class MockClient extends Mock implements http.Client {}

void main() {
  enableFlutterDriverExtension();

  final MockClient client = MockClient();
  // make your mocks here
  httpClient = client;

  runApp(app.MyApp());
}

由于模拟所有请求可能会变成一个巨大的代码，因此您可以创建一个单独的函数，以便更好地组织代码：

import 'package:flutter/widgets.dart';
import 'package:flutter_driver/driver_extension.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:utgard/business/config/globals.dart';
import 'package:utgard/main.dart' as app;

class MockClient extends Mock implements http.Client {}

void main() {
  enableFlutterDriverExtension();

  final MockClient client = MockClient();
  makeMock();
  httpClient = client;

  runApp(app.MyApp());
}