具有模拟和协程的 Android 测试存储库返回 NullPointerException

Question

我有点困惑我应该如何测试它

我有这个存储库类:

class AuthenticationBox(
    private val dataMapper: AuthenticationDataMapper,
    private val dataSource: AuthenticationDataSource
) : BaseRepository<UserAuthentication>(), AuthenticationRepository {

override suspend fun fetchAuthenticationFromServer(
        username: String,
        password: String
    ): ResourceResult<UserAuthentication>? {
        var result: ResourceResult<UserAuthentication>? = null

        withContext(Dispatchers.IO) {
            try {
                val response = dataSource
                    .fetchAuthenticationFromServerAsync(username, password).await()

                if (response.hasErrors()) {
                    result =
                        ResourceResult.Error(ApolloException(response.errors()[0].message()))

                } else {
                    response.data()?.let {
                        val authorization = dataMapper.toDomain(it.loginResponse)

                        result = ResourceResult.Success(authorization)
                    }

                }

            } catch (error: ApolloException) {
                result = handleAuthenticationError(error)
            }
        }
        return result

    }


}

这一行调用了一个返回 Deferred<Response> 的数据源方法对象并等待它 val response = dataSource.fetchAuthenticationFromServerAsync(username, password).await()

当我尝试测试它时，我总是得到一个 NullPointerException正好在这条线上
这是我的测试类:

class AuthenticationBoxTest {

    lateinit var repository: AuthenticationRepository

    var dataSourceMock: AuthenticationDataSource = mock()
    var dataMapperMock: AuthenticationDataMapper = mock()


   @Before
    fun setup() {
        repository = AuthenticationBox(
            dataMapper = dataMapperMock,
            dataSource = dataSourceMock
        )
    }

     @Test
    fun testFromServer() {
        val username = "username"
        val password = "password"
        runBlocking {
            repository.fetchAuthenticationFromServer(username, password)
        }
    }

}

日志输出为:

java.lang.NullPointerException
    at br.com.ampli.authentication.repository.AuthenticationBox$fetchAuthenticationFromServer$2.invokeSuspend(AuthenticationBox.kt:45)
    at |b|b|b(Coroutine boundary.|b(|b)
    at br.com.ampli.authentication.repository.AuthenticationBox.fetchAuthenticationFromServer(AuthenticationBox.kt:42)
    at br.com.ampli.authentication.repository.AuthenticationBoxTest$testFromServer$1.invokeSuspend(AuthenticationBoxTest.kt:126)
Caused by: java.lang.NullPointerException
    at br.com.ampli.authentication.repository.AuthenticationBox$fetchAuthenticationFromServer$2.invokeSuspend(AuthenticationBox.kt:45)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241)
    at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
    at kotlinx.coroutines.scheduling.CoroutineScheduler.access$runSafely(CoroutineScheduler.kt:60)
    at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:740)

我在这个存储库类上的所有其他功能都是暂停功能，并且都使用 withContext(Dispatchers.IO)并且我能够对它们进行全部测试(其中任何一个都称为另一个类)。这是唯一给我这个错误的。

在此先感谢您对此的任何见解。

Answer 1

您的 mock() 可能有错误。您确定数据源模拟有一个返回该方法的延迟的实现吗？

.fetchAuthenticationFromServerAsync(username, password)

This medium post有一个模拟方法返回延迟的示例，它会为您的用例提供类似这样的内容:

//a small helper function first
fun <T> T.toDeferred() = GlobalScope.async { this@toDeferred }

val authResult = dummyAuthDataSourceResult  //dummy result
val mockedDatasource = mock<AuthenticationDataSource> {    
      on { fetchAuthenticationFromServerAsync() } doReturn authResult.toDeferred()
}

现在您应该可以安全地调用:

mockedDatasource.fetchAuthenticationFromServerAsync().await()