我一直在使用Google的拱库，但是使测试变得困难的一件事就是使用PagedList。
对于此示例，我使用存储库模式并从API或网络返回详细信息。
因此，在ViewModel中，我调用了这个接口方法：
override fun getFoos(): Observable<PagedList<Foo>>
然后，存储库将使用RxPagedListBuilder创建类型为PagedList的Observable：
override fun getFoos(): Observable<PagedList<Foo>> =
RxPagedListBuilder(database.fooDao().selectAll(), PAGED_LIST_CONFIG).buildObservable()
我希望测试可以从这些返回PagedList<Foo>的方法设置返回值。类似于
when(repository.getFoos()).thenReturn(Observable.just(TEST_PAGED_LIST_OF_FOOS)
两个问题：
PagedList<Foo>？我的目标是以更加端到端的方式进行验证（例如确保在屏幕上显示正确的Foos列表）。片段/活动/视图是从ViewModel观察PagedList<Foo>的那个。
答案 0 :(得分：4)
实现此目的的一种简单方法是模拟PagedList。这种有趣的操作会将列表“转换”为PagedList（在这种情况下，我们使用的不是真正的PagedList，而只是模拟版本，如果需要实现PagedList的其他方法，请在此方法中添加它们）
fun <T> mockPagedList(list: List<T>): PagedList<T> {
val pagedList = Mockito.mock(PagedList::class.java) as PagedList<T>
Mockito.`when`(pagedList.get(ArgumentMatchers.anyInt())).then { invocation ->
val index = invocation.arguments.first() as Int
list[index]
}
Mockito.`when`(pagedList.size).thenReturn(list.size)
return pagedList
}
答案 1 :(得分：0)
如果这是一个端到端测试，则可以只使用内存数据库。在调用之前添加测试数据。例： https://medium.com/exploring-android/android-architecture-components-testing-your-room-dao-classes-e06e1c9a1535
答案 2 :(得分：0)
@saied89在本solution期中共享了此googlesamples/android-architecture-components。我已经在Coinverse Open App中实现了模拟的PagedList，以便使用Kotlin，JUnit 5，MockK和AssertJ库对ViewModel进行本地单元测试。
要观察PagedList中的LiveData，我在Google的Android体系结构组件示例下使用了Jose Alcérreca's中getOrAwaitValue中的implementation LiveDataSample sample app。
asPagedList扩展功能在下面的示例测试 ContentViewModelTest.kt 中实现。
PagedListTestUtil.kt
import android.database.Cursor
import androidx.paging.DataSource
import androidx.paging.LivePagedListBuilder
import androidx.paging.PagedList
import androidx.room.RoomDatabase
import androidx.room.RoomSQLiteQuery
import androidx.room.paging.LimitOffsetDataSource
import io.mockk.every
import io.mockk.mockk
fun <T> List<T>.asPagedList() = LivePagedListBuilder<Int, T>(createMockDataSourceFactory(this),
Config(enablePlaceholders = false,
prefetchDistance = 24,
pageSize = if (size == 0) 1 else size))
.build().getOrAwaitValue()
private fun <T> createMockDataSourceFactory(itemList: List<T>): DataSource.Factory<Int, T> =
object : DataSource.Factory<Int, T>() {
override fun create(): DataSource<Int, T> = MockLimitDataSource(itemList)
}
private val mockQuery = mockk<RoomSQLiteQuery> {
every { sql } returns ""
}
private val mockDb = mockk<RoomDatabase> {
every { invalidationTracker } returns mockk(relaxUnitFun = true)
}
class MockLimitDataSource<T>(private val itemList: List<T>) : LimitOffsetDataSource<T>(mockDb, mockQuery, false, null) {
override fun convertRows(cursor: Cursor?): MutableList<T> = itemList.toMutableList()
override fun countItems(): Int = itemList.count()
override fun isInvalid(): Boolean = false
override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<T>) { /* Not implemented */ }
override fun loadRange(startPosition: Int, loadCount: Int) =
itemList.subList(startPosition, startPosition + loadCount).toMutableList()
override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<T>) {
callback.onResult(itemList, 0)
}
}
LiveDataTestUtil.kt
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
import java.util.concurrent.CountDownLatch
import java.util.concurrent.TimeUnit
import java.util.concurrent.TimeoutException
/**
* Gets the value of a [LiveData] or waits for it to have one, with a timeout.
*
* Use this extension from host-side (JVM) tests. It's recommended to use it alongside
* `InstantTaskExecutorRule` or a similar mechanism to execute tasks synchronously.
*/
fun <T> LiveData<T>.getOrAwaitValue(
time: Long = 2,
timeUnit: TimeUnit = TimeUnit.SECONDS,
afterObserve: () -> Unit = {}
): T {
var data: T? = null
val latch = CountDownLatch(1)
val observer = object : Observer<T> {
override fun onChanged(o: T?) {
data = o
latch.countDown()
this@getOrAwaitValue.removeObserver(this)
}
}
this.observeForever(observer)
afterObserve.invoke()
// Don't wait indefinitely if the LiveData is not set.
if (!latch.await(time, timeUnit)) {
this.removeObserver(observer)
throw TimeoutException("LiveData value was never set.")
}
@Suppress("UNCHECKED_CAST")
return data as T
}
ContentViewModelTest.kt
...
import androidx.paging.PagedList
import com.google.firebase.Timestamp
import io.mockk.*
import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.AfterAll
import org.junit.jupiter.api.BeforeAll
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.extension.ExtendWith
@ExtendWith(InstantExecutorExtension::class)
class ContentViewModelTest {
val timestamp = getTimeframe(DAY)
@BeforeAll
fun beforeAll() {
mockkObject(ContentRepository)
}
@BeforeEach
fun beforeEach() {
clearAllMocks()
}
@AfterAll
fun afterAll() {
unmockkAll()
}
@Test
fun `Feed Load`() {
val content = Content("85", 0.0, Enums.ContentType.NONE, Timestamp.now(), "",
"", "", "", "", "", "", MAIN,
0, 0.0, 0.0, 0.0, 0.0,
0.0, 0.0, 0.0, 0.0)
every {
getMainFeedList(any(), any())
} returns liveData {
emit(Lce.Content(
ContentResult.PagedListResult(
pagedList = liveData {emit(listOf(content).asPagedList())},
errorMessage = ""))
}
val contentViewModel = ContentViewModel(ContentRepository)
contentViewModel.processEvent(ContentViewEvent.FeedLoad(MAIN, DAY, timestamp, false))
assertThat(contentViewModel.feedViewState.getOrAwaitValue().contentList.getOrAwaitValue()[0])
.isEqualTo(content)
assertThat(contentViewModel.feedViewState.getOrAwaitValue().toolbar).isEqualTo(
ToolbarState(
visibility = GONE,
titleRes = app_name,
isSupportActionBarEnabled = false))
verify {
getMainFeedList(any(), any())
}
confirmVerified(ContentRepository)
}
}
InstantExecutorExtension.kt
使用LiveData时，这对于JUnit 5是必需的，以确保Observer不在主线程上。以下是Jeroen Mols' implementation。
import androidx.arch.core.executor.ArchTaskExecutor
import androidx.arch.core.executor.TaskExecutor
import org.junit.jupiter.api.extension.AfterEachCallback
import org.junit.jupiter.api.extension.BeforeEachCallback
import org.junit.jupiter.api.extension.ExtensionContext
class InstantExecutorExtension : BeforeEachCallback, AfterEachCallback {
override fun beforeEach(context: ExtensionContext?) {
ArchTaskExecutor.getInstance().setDelegate(object : TaskExecutor() {
override fun executeOnDiskIO(runnable: Runnable) = runnable.run()
override fun postToMainThread(runnable: Runnable) = runnable.run()
override fun isMainThread(): Boolean = true
})
}
override fun afterEach(context: ExtensionContext?) {
ArchTaskExecutor.getInstance().setDelegate(null)
}
}