Mockito无法Mock isOnline方法，测试触发真实网络校验报错求助

你用Mockito mock isOnline 方法无效，核心原因是该方法是目标类（sut）的非open成员方法。Mockito默认基于动态代理实现mock，只能处理接口或标记为open的类/方法；普通final方法（Kotlin默认方法为final）会绕过mock逻辑，直接执行真实的网络校验代码，导致测试报错。

方案一：重构代码，抽离网络校验依赖（推荐） #

将网络判断逻辑从ViewModel中剥离为独立工具类，通过依赖注入引入，这样可以完全隔离真实网络逻辑，测试时直接mock这个工具类即可。

1. 新建网络工具类 #

class NetworkConnectivityHelper(private val context: Context) {
    fun isOnline(): Boolean {
        val connectivityManager =
            context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

        val capabilities =
            connectivityManager.getNetworkCapabilities(connectivityManager.activeNetwork)
        if (capabilities != null) {
            if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
                return true
            } else if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
                return true
            }
        }
        return false
    }
}

2. 修改ViewModel，注入工具类 #

class YourViewModel(
    private val networkHelper: NetworkConnectivityHelper,
    private val getCharactersFromDataBaseUseCase: GetCharactersFromDataBaseUseCase,
    private val getAllCharactersUseCase: GetAllCharactersUseCase
) : ViewModel() {
    private val _getAllCharactersResponseLiveData = MutableLiveData<Resource<List<Character>>>()
    val getAllCharactersLiveData: LiveData<Resource<List<Character>>> = _getAllCharactersResponseLiveData

    fun getAllCharacters() = viewModelScope.launch {
        _getAllCharactersResponseLiveData.postValue(Resource.Loading())
        val charactersList = getCharactersFromDataBaseUseCase.getAllCharactersFromDataBase()

        if (networkHelper.isOnline() && charactersList.isEmpty()) {
            _getAllCharactersResponseLiveData.postValue(getAllCharactersUseCase.getAllCharacters())
        } else if (!networkHelper.isOnline() && charactersList.isNotEmpty() ||
            networkHelper.isOnline() && charactersList.isNotEmpty()
        ) {
            _getAllCharactersResponseLiveData.postValue(
                Resource.Success(
                    getCharactersFromDataBaseUseCase.getAllCharactersFromDataBase()
                )
            )
        } else {
            _getAllCharactersResponseLiveData.postValue(Resource.Error())
        }
    }
}

3. 测试代码中mock工具类 #

@Test
fun internet_connected_and_empty_data_base_gets_info_from_api_success() {
    // given
    val mockNetworkHelper = mock(NetworkConnectivityHelper::class.java)
    `when`(mockNetworkHelper.isOnline()).thenReturn(true)
    // mock其他依赖的返回值
    `when`(getCharactersFromDataBaseUseCase.getAllCharactersFromDataBase()).thenReturn(emptyList())
    `when`(getAllCharactersUseCase.getAllCharacters()).thenReturn(Resource.Success(listOf(Character(name = "char1"))))
    
    val sut = YourViewModel(mockNetworkHelper, getCharactersFromDataBaseUseCase, getAllCharactersUseCase)

    // when
    sut.getAllCharacters()
    val expected = sut.getAllCharactersLiveData.getOrAwaitValue().data

    // then
    assertThat(expected?.first()?.name).isEqualTo("char1")
}

方案二：用Mockito Spy做部分mock（临时 workaround） #

如果不想重构代码，可以用Spy创建目标类的部分mock实例，但需要先把isOnline方法改为open（因为Kotlin默认方法是final，Spy无法代理）。

1. 修改ViewModel的isOnline方法为open #

open fun isOnline(context: Context): Boolean {
    // 原逻辑保持不变
}

2. 测试代码使用Spy #

@Test
fun internet_connected_and_empty_data_base_gets_info_from_api_success() {
    // given
    val sut = spy(YourViewModel(...)) // 传入构造所需的其他依赖
    `when`(sut.isOnline(context)).thenReturn(true)
    // mock其他依赖的返回值
    `when`(getCharactersFromDataBaseUseCase.getAllCharactersFromDataBase()).thenReturn(emptyList())
    `when`(getAllCharactersUseCase.getAllCharacters()).thenReturn(Resource.Success(listOf(Character(name = "char1"))))

    // when
    sut.getAllCharacters()
    val expected = sut.getAllCharactersLiveData.getOrAwaitValue().data

    // then
    assertThat(expected?.first()?.name).isEqualTo("char1")
}

• 方案一符合SOLID原则，降低ViewModel职责，后续测试、维护更灵活，是长期最优解。
• 方案二属于临时修复，需要修改方法的访问修饰符，破坏封装性，仅适合快速验证场景。

内容的提问来源于stack exchange，提问作者Tony