问题
I have been working with the arch libraries from Google, but one thing that has made testing difficult is working with PagedList.
For this example, I am using the repository pattern and returning details from either an API or network.
So within the ViewModel I make a call to this interface method:
override fun getFoos(): Observable<PagedList<Foo>>
The Repository will then use RxPagedListBuilder to create the Observable that is of type PagedList:
override fun getFoos(): Observable<PagedList<Foo>> =
RxPagedListBuilder(database.fooDao().selectAll(), PAGED_LIST_CONFIG).buildObservable()
I want to be able for tests to setup the return from these methods that return a PagedList<Foo>. Something similar to
when(repository.getFoos()).thenReturn(Observable.just(TEST_PAGED_LIST_OF_FOOS)
Two questions:
- Is this possible?
- How do I create a
PagedList<Foo>?
My goal is to verify in a more end-to-end fashion (such as ensuring that the correct list of Foos is displayed on the screen). The fragment/activity/view is the one observing the PagedList<Foo> from a ViewModel.
回答1:
an easy way to achieve this, is to mock the PagedList. This fun will "convert" a list to a PagedList (in this case, we are not using the real PagedList rather just a mocked version, if you need other methods of PagedList to be implemented, add them in this fun)
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
}
回答2:
- You cannot cast List to PagedList.
- You cannot create PagedList directly, only through DataSource. One way is creating FakeDataSource returning the test data.
If it is an end-to-end test, you could just use in-memory db. Add your test data before calling it. Example: https://medium.com/exploring-android/android-architecture-components-testing-your-room-dao-classes-e06e1c9a1535
回答3:
Convert List Into PagedList With Mock DataSource.Factory
@saied89 shared this solution in this googlesamples/android-architecture-components issue. I've implemented the mocked PagedList in the Coinverse Open App in order to local unit test a ViewModel using Kotlin, JUnit 5, MockK, and AssertJ libraries.
To observe the LiveData from the PagedList I've used Jose Alcérreca's implementation of getOrAwaitValue from the LiveDataSample sample app under Google's Android Architecture Components samples.
The asPagedList extension function is implemented in the sample test ContentViewModelTest.kt below.
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
This is required for JUnit 5 when using LiveData in order to ensure the Observer is not on the main thread. Below is 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)
}
}
来源：https://stackoverflow.com/questions/50435770/how-do-i-create-a-pagedlist-of-an-object-for-tests