Android 如何从第3页测试分页数据

MyViewModel有一个返回分页数据流的方法。在我的应用程序中，数据从远程服务器获取，然后保存到房间（真相的单一来源）：

---

我想知道我是否在正确的轨道上。任何帮助都将不胜感激

基本上有两种方法，这取决于您想要转换前还是转换后的数据

如果您只想断言存储库端，那么您的查询是正确的-您可以直接查询

PagingSource

，这是预转换，尽管如此，您对ViewModel中的PagingData所做的任何映射或筛选都不会在这里被考虑。但是，如果您想直接测试查询，它更“纯粹”

@Test
fun repo() = runBlockingTest {
  val pagingSource = MyPagingSource()
  val loadResult = pagingSource.load(...)
  assertEquals(
    expected = LoadResult.Page(...),
    actual = loadResult,
  )
}

另一种方法是，如果您关心转换，则需要将数据从

PagingData

加载到presenter API中

@Test
fun ui() = runBlockingTest {
  val viewModel = ... // Some AndroidX Test rules can help you here, but also some people choose to do it manually.
  val adapter = MyAdapter(..)

  // You need to launch here because submitData suspends forever while PagingData is alive
  val job = launch {
    viewModel.flow.collectLatest {
      adapter.submitData(it)
    }
  }

  ... // Do some stuff to trigger loads
  advanceUntilIdle() // Let test dispatcher resolve everything

  // How to read from adapter state, there is also .peek() and .itemCount
  assertEquals(..., adapter.snapshot())

  // We need to cancel the launched job as coroutines.test framework checks for leaky jobs
  job.cancel()
}

我发现使用会容易得多

根据您的代码，我认为您的测试用例应该如下所示：

@ExperimentalTime
@ExperimentalCoroutinesApi
@Test
fun `test if receive paged chocolate data`() = runBlockingTest {

    val expected = listOf(
      Chocolate(name = "Dove"),
      Chocolate(name = "Hershey's")
    )

    coEvery {
        dao().getChocolateListData()
    }.returns(
        listOf(
            Chocolate(name = "Dove"),
            Chocolate(name = "Hershey's")
        )
    )

    launchTest {
        viewModel.getChocolates().test(
            timeout = Duration.ZERO,
            validate = {
                val collectedData = expectItem().collectData()
                assertEquals(expected, collectedData)
                expectComplete()
            })
    }
}

我还准备了一个基本ViewModelTest类，用于处理许多设置和拆卸任务：

abstract class BaseViewModelTest {
    @get:Rule
    open val instantTaskExecutorRule = InstantTaskExecutorRule()

    @get:Rule
    open val testCoroutineRule = CoroutineTestRule()

    @MockK
    protected lateinit var owner: LifecycleOwner

    private lateinit var lifecycle: LifecycleRegistry

    @Before
    open fun setup() {
        MockKAnnotations.init(this)

        lifecycle = LifecycleRegistry(owner)
        every { owner.lifecycle } returns lifecycle
    }

    @After
    fun tearDown() {
        clearAllMocks()
    }

    protected fun initCoroutine(vm: BaseViewModel) {
        vm.apply {
            setViewModelScope(testCoroutineRule.testCoroutineScope)
            setCoroutineContext(testCoroutineRule.testCoroutineDispatcher)
        }
    }

    @ExperimentalCoroutinesApi
    protected fun runBlockingTest(block: suspend TestCoroutineScope.() -> Unit) =
        testCoroutineRule.runBlockingTest(block)


    protected fun launchTest(block: suspend TestCoroutineScope.() -> Unit) =
        testCoroutineRule.testCoroutineScope.launch(testCoroutineRule.testCoroutineDispatcher) { block }

}

至于借用的扩展函数

collectData（）

（谢谢！！）

---

还有一个幻灯片介绍了

关于PagingData，您想断言/测试什么？我已经更新了我的问题。PagingData（Paging3版本3.0.0.rc01）、单元测试（JUnit4）谢谢您的回答。在测试Dao查询时，我已经执行了PagingSource查询。我必须在存储库层再次测试它吗？同样，我不想处理存储库测试中的UI，因此我不想采用后一种方法。如果要测试

Pager.flow

的输出，包括任何转换，则需要某种方法来断言

PagingData

的输出。由于整个事件流都是内部的，所以唯一的方法是将其收集到某个presenter API中。这并不一定意味着UI，但您确实需要

PagingDataAdapter

或

AsyncPagingDataDifference

的实例。更好的测试UTIL取代这些是一个WIP FR，用于将来的分页版本，可能会作为一个单独的模块出现。再次感谢您的回答。我已经更新了我目前的进度。但是，adapter.snapshot（）似乎是空的。Dao插入操作是否可以触发加载？我的想法是它可以，因为分页库在后台使用流API。此外，我在哪里可以了解这个WIP FR？提前谢谢。很抱歉，我没有在这里看到你的答复-希望我不会太晚。您正在使用

runBlockingTest

，我看不到从哪里提供

chocolateListAdapter

，但您需要等待实际加载本身，并在执行断言之前让它完成。e、 例如，将

TestCoroutineDispatcher

传递给fetch/main dispatcher并调用

advanceUntilIdle（）

testImplementation "app.cash.turbine:turbine:0.2.1"

@ExperimentalTime
@ExperimentalCoroutinesApi
@Test
fun `test if receive paged chocolate data`() = runBlockingTest {

    val expected = listOf(
      Chocolate(name = "Dove"),
      Chocolate(name = "Hershey's")
    )

    coEvery {
        dao().getChocolateListData()
    }.returns(
        listOf(
            Chocolate(name = "Dove"),
            Chocolate(name = "Hershey's")
        )
    )

    launchTest {
        viewModel.getChocolates().test(
            timeout = Duration.ZERO,
            validate = {
                val collectedData = expectItem().collectData()
                assertEquals(expected, collectedData)
                expectComplete()
            })
    }
}

abstract class BaseViewModelTest {
    @get:Rule
    open val instantTaskExecutorRule = InstantTaskExecutorRule()

    @get:Rule
    open val testCoroutineRule = CoroutineTestRule()

    @MockK
    protected lateinit var owner: LifecycleOwner

    private lateinit var lifecycle: LifecycleRegistry

    @Before
    open fun setup() {
        MockKAnnotations.init(this)

        lifecycle = LifecycleRegistry(owner)
        every { owner.lifecycle } returns lifecycle
    }

    @After
    fun tearDown() {
        clearAllMocks()
    }

    protected fun initCoroutine(vm: BaseViewModel) {
        vm.apply {
            setViewModelScope(testCoroutineRule.testCoroutineScope)
            setCoroutineContext(testCoroutineRule.testCoroutineDispatcher)
        }
    }

    @ExperimentalCoroutinesApi
    protected fun runBlockingTest(block: suspend TestCoroutineScope.() -> Unit) =
        testCoroutineRule.runBlockingTest(block)


    protected fun launchTest(block: suspend TestCoroutineScope.() -> Unit) =
        testCoroutineRule.testCoroutineScope.launch(testCoroutineRule.testCoroutineDispatcher) { block }

}