Develop Reference

How to test Android Room Transactions with Flowables and Coroutines

Background
I've got the below test where I'm trying to observe (RxJava Flowable) the change in count of items in a table once inserts (coroutines/suspend) are performed in a transaction:
#RunWith(AndroidJUnit4::class)
class Test {
#get:Rule var instantTaskExecutorRule = InstantTaskExecutorRule()
private lateinit var database: Database
private lateinit var transactionManager: TransactionManager
#Before
fun createDatabase() {
database = Room.inMemoryDatabaseBuilder(
ApplicationProvider.getApplicationContext(),
Database::class.java
)
.setTransactionExecutor(Executors.newSingleThreadExecutor()) // To avoid transaction deadlock
.build()
}
#After
fun closeDb() {
database.close()
}
#Test
fun getCountChanges_whenItemInserted_shouldUpdateCount(): Unit = runBlocking {
// getCountChanges() returns Flowable<Int>
val subscriber = database.item().getCountChanges().take(2).test()
val callable = suspend {
database.node().insert(NodeDO("id1")) // standard dao method marked with suspend
database.item().insert(ItemDO("id1")) // standard dao method marked with suspend
}
transactionManager.runInTransaction(callable) // just calling db.withTransaction(callable)
subscriber.assertComplete() // Test fails here - not complete ****
subscriber.assertNoErrors()
subscriber.assertValueCount(2)
assertThat(subscriber.values().first()).isEqualTo(0)
assertThat(subscriber.values().last()).isEqualTo(1)
subscriber.dispose()
}
}
Test Results
If I run the test as is, the test fails (as marked at the spot in the code above) saying that the subscriber is not complete.
If I remove the .setTransactionExecutor(Executors.newSingleThreadExecutor()) line, the test gets deadlocked and never finishes.
If I remove the transaction, and execute the two inserts independently, the test passes successfully.
Question
How can I successfully test this situation using a transaction?

How To Test PagingData From Paging 3

My ViewModel has a method which returns a flow of PagingData. In my app, the data is fetched from the remote server, which is then saved to Room (the single source of truth):
fun getChocolates(): Flow<PagingData<Chocolate>> {
val pagingSourceFactory = { dao().getChocolateListData() }
return Pager(
config = PagingConfig(
pageSize = NETWORK_PAGE_SIZE,
maxSize = MAX_MEMORY_SIZE,
enablePlaceholders = false
),
remoteMediator = ChocolateRemoteMediator(
api,
dao
),
pagingSourceFactory = pagingSourceFactory
).flow
}
How do I test this method? I want to test if the returning flow contains the correct data.
What I've tried so far:
#InternalCoroutinesApi
#Test
fun getChocolateListReturnsCorrectData() = runBlockingTest {
val chocolateListDao: ChocolateListDao by inject()
val chocolatesRepository: ChocolatesRepository by inject()
val chocolateListAdapter: ChocolateListAdapter by inject()
// 1
val chocolate1 = Chocolate(
name = "Dove"
)
val chocolate2 = Chocolate(
name = "Hershey's"
)
// 2
// You need to launch here because submitData suspends forever while PagingData is alive
val job = launch {
chocolatesRepository.getChocolateListStream().collectLatest {
chocolateListAdapter.submitData(it)
}
}
// Do some stuff to trigger loads
chocolateListDao.saveChocolate(chocolate1, chocolate2)
// How to read from adapter state, there is also .peek() and .itemCount
assertEquals(listOf(chocolate1, chocolate2).toMutableList(), chocolateListAdapter.snapshot())
// We need to cancel the launched job as coroutines.test framework checks for leaky jobs
job.cancel()
}
I'm wondering if I'm on the right track. Any help would be greatly appreciated!

I found using Turbine from cashapp would be much much easier.(JakeWharton comes to rescue again :P)
testImplementation "app.cash.turbine:turbine:0.2.1"
According to your code I think your test case should looks like:
#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()
})
}
}
I also prepare a base ViewModelTest class for taking care of much of setup and tearDown tasks:
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 }
}
As for extension function collectData() that's borrowed from answer from another post (Thanks #Farid!!)
And a slide show introducing turbine

There's basically two approaches to this depending on if you want pre-transformation or post-transformation data.
If you want to just assert the repository end, that your query is correct - you can just query PagingSource directly, this is pre-transform though so any mapping you do or filtering you do to PagingData in ViewModel won't be accounted for here. However, it's more "pure" if you want to test the query directly.
#Test
fun repo() = runBlockingTest {
val pagingSource = MyPagingSource()
val loadResult = pagingSource.load(...)
assertEquals(
expected = LoadResult.Page(...),
actual = loadResult,
)
}
The other way if you care about transforms, you need to load data from PagingData into a presenter API.
#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()
}

Suspending function test with MockWebServer

I'm testing api that returns result using suspending function with MockWebServer, but it does not work with runBlockingTest, testCoroutineDispatcher, testCorounieScope unless a launch builder is used, why?
abstract class AbstractPostApiTest {
internal lateinit var mockWebServer: MockWebServer
private val responseAsString by lazy {
getResourceAsText(RESPONSE_JSON_PATH)
}
#BeforeEach
open fun setUp() {
mockWebServer = MockWebServer()
println("AbstractPostApiTest setUp() $mockWebServer")
}
#AfterEach
open fun tearDown() {
mockWebServer.shutdown()
}
companion object {
const val RESPONSE_JSON_PATH = "posts.json"
}
#Throws(IOException::class)
fun enqueueResponse(
code: Int = 200,
headers: Map<String, String>? = null
): MockResponse {
// Define mock response
val mockResponse = MockResponse()
// Set response code
mockResponse.setResponseCode(code)
// Set headers
headers?.let {
for ((key, value) in it) {
mockResponse.addHeader(key, value)
}
}
// Set body
mockWebServer.enqueue(
mockResponse.setBody(responseAsString)
)
return mockResponse
}
}
class PostApiTest : AbstractPostApiTest() {
private lateinit var postApi: PostApiCoroutines
private val testCoroutineDispatcher = TestCoroutineDispatcher()
private val testCoroutineScope = TestCoroutineScope(testCoroutineDispatcher)
#BeforeEach
override fun setUp() {
super.setUp()
val okHttpClient = OkHttpClient
.Builder()
.build()
postApi = Retrofit.Builder()
.baseUrl(mockWebServer.url("/"))
.addConverterFactory(GsonConverterFactory.create())
.client(okHttpClient)
.build()
.create(PostApiCoroutines::class.java)
Dispatchers.setMain(testCoroutineDispatcher)
}
#AfterEach
override fun tearDown() {
super.tearDown()
Dispatchers.resetMain()
try {
testCoroutineScope.cleanupTestCoroutines()
} catch (exception: Exception) {
exception.printStackTrace()
}
}
#Test
fun `Given we have a valid request, should be done to correct url`() =
testCoroutineScope.runBlockingTest {
// GIVEN
enqueueResponse(200, RESPONSE_JSON_PATH)
// WHEN
postApi.getPostsResponse()
advanceUntilIdle()
val request = mockWebServer.takeRequest()
// THEN
Truth.assertThat(request.path).isEqualTo("/posts")
}
}
Results error: java.lang.IllegalStateException: This job has not completed yet
This test does not work if launch builder is used, and if launch builder is used it does not require testCoroutineDispatcher or testCoroutineScope, what's the reason for this? Normally suspending functions pass without being in another scope even with runBlockingTest
#Test
fun `Given we have a valid request, should be done to correct url`() =
runBlockingTest {
// GIVEN
enqueueResponse(200, RESPONSE_JSON_PATH)
// WHEN
launch {
postApi.getPosts()
}
val request = mockWebServer.takeRequest()
// THEN
Truth.assertThat(request.path).isEqualTo("/posts")
}
The one above works.
Also the test below pass some of the time.
#Test
fun Given api return 200, should have list of posts() =
testCoroutineScope.runBlockingTest {
// GIVEN
enqueueResponse(200)
// WHEN
var posts: List<Post> = emptyList()
launch {
posts = postApi.getPosts()
}
advanceUntilIdle()
// THEN
Truth.assertThat(posts).isNotNull()
Truth.assertThat(posts.size).isEqualTo(100)
}
I tried many combinations invoking posts = postApi.getPosts() without launch, using async, putting enqueueResponse(200) inside async async { enqueueResponse(200) }.await() but tests failed, sometimes it pass sometimes it does not some with each combination.

There is a bug with runBlockTest not waiting for other threads/jobs to complete before completing the coroutine that the test is running in.
I tried using runBlocking with success (I use the awesome port of Hamcrest to Kotlin Hamkrest)
fun `run test` = runBlocking {
mockWebServer.enqueue(MockResponse().setResponseCode(200).setBody(""))
// make HTTP call
val result = mockWebServer.takeRequest(2000L, TimeUnit.MILLISECONDS)
assertThat(result != null, equalTo(true))
}
There's a few things to note here:
The use of thread blocking calls should never be called without a timeout. Always better to fail with nothing, then to block a thread forever.
The use of runBlocking might be considered by some to be no no. However this blog post outlines the different method of running concurrent code, and the different use cases for them. We normally want to use runBlockingTest or (TestCoroutineDispatcher.runBlockingTest) so that our test code and app code are synchronised. By using the same Dispatcher we can make sure that the jobs all finish, etc. TestCoroutineDispatcher also has that handy "clock" feature to make delays disappear. However when testing the HTTP layer of the application, and where there is a mock server running on a separate thread we have a synchronisation point being takeRequest. So we can happily use runBlocking to allow us to use coroutines and a mock server running on a different thread work together with no problems.

Unit testing coroutines runBlockingTest: This job has not completed yet

Please find below a function using a coroutine to replace callback :
override suspend fun signUp(authentication: Authentication): AuthenticationError {
return suspendCancellableCoroutine {
auth.createUserWithEmailAndPassword(authentication.email, authentication.password)
.addOnCompleteListener(activityLifeCycleService.getActivity()) { task ->
if (task.isSuccessful) {
it.resume(AuthenticationError.SignUpSuccess)
} else {
Log.w(this.javaClass.name, "createUserWithEmail:failure", task.exception)
it.resume(AuthenticationError.SignUpFail)
}
}
}
}
Now I would like to unit testing this function. I am using Mockk :
#Test
fun `signup() must be delegated to createUserWithEmailAndPassword()`() = runBlockingTest {
val listener = slot<OnCompleteListener<AuthResult>>()
val authentication = mockk<Authentication> {
every { email } returns "email"
every { password } returns "pswd"
}
val task = mockk<Task<AuthResult>> {
every { isSuccessful } returns true
}
every { auth.createUserWithEmailAndPassword("email", "pswd") } returns
mockk {
every { addOnCompleteListener(activity, capture(listener)) } returns mockk()
}
service.signUp(authentication)
listener.captured.onComplete(task)
}
Unfortunately this test failed due to the following exception : java.lang.IllegalStateException: This job has not completed yet
I tried to replace runBlockingTest with runBlocking but the test seems to wait in an infinite loop.
Can someone help me with this UT please?
Thanks in advance

As can be seen in this post:
This exception usually means that some coroutines from your tests were scheduled outside the test scope (more specifically the test dispatcher).
Instead of performing this:
private val networkContext: CoroutineContext = TestCoroutineDispatcher()
private val sut = Foo(
networkContext,
someInteractor
)
fun `some test`() = runBlockingTest() {
// given
...
// when
sut.foo()
// then
...
}
Create a test scope passing test dispatcher:
private val testDispatcher = TestCoroutineDispatcher()
private val testScope = TestCoroutineScope(testDispatcher)
private val networkContext: CoroutineContext = testDispatcher
private val sut = Foo(
networkContext,
someInteractor
)
Then in test perform testScope.runBlockingTest
fun `some test`() = testScope.runBlockingTest {
...
}
See also Craig Russell's "Unit Testing Coroutine Suspend Functions using TestCoroutineDispatcher"

In case of Flow testing:
Don't use flow.collect directly inside runBlockingTest. It should be wrapped in launch
Don't forget to cancel TestCoroutineScope in the end of a test. It will stop a Flow collecting.
Example:
class CoroutinesPlayground {
private val job = Job()
private val testDispatcher = StandardTestDispatcher()
private val testScope = TestScope(job + testDispatcher)
#Test
fun `play with coroutines here`() = testScope.runBlockingTest {
val flow = MutableSharedFlow<Int>()
launch {
flow.collect { value ->
println("Value: $value")
}
}
launch {
repeat(10) { value ->
flow.emit(value)
delay(1000)
}
job.cancel()
}
}
}

This is not an official solution, so use it at your own risk.
This is similar to what #azizbekian posted, but instead of calling runBlocking, you call launch.
As this is using TestCoroutineDispatcher, any tasks scheduled to be run without delay are immediately executed. This might not be suitable if you have several tasks running asynchronously.
It might not be suitable for every case but I hope that it helps for simple cases.
You can also follow up on this issue here:
https://github.com/Kotlin/kotlinx.coroutines/issues/1204
If you know how to solve this using the already existing runBlockingTest and runBlocking, please be so kind and share with the community.
class MyTest {
private val dispatcher = TestCoroutineDispatcher()
private val testScope = TestCoroutineScope(dispatcher)
#Test
fun myTest {
val apiService = mockk<ApiService>()
val repository = MyRepository(apiService)
testScope.launch {
repository.someSuspendedFunction()
}
verify { apiService.expectedFunctionToBeCalled() }
}
}

According to my understanding, this exception occurs when you are using a different dispatcher in your code inside the runBlockingTest { } block with the one that started runBlockingTest { }.
So in order to avoid this, you first have to make sure you inject Dispatchers in your code, instead of hardcoding it throughout your app. If you haven't done it, there's nowhere to begin because you cannot assign a test dispatcher to your test codes.
Then, in your BaseUnitTest, you should have something like this:
#get:Rule
val coroutineRule = CoroutineTestRule()
#ExperimentalCoroutinesApi
class CoroutineTestRule(
val testDispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()
) : TestWatcher() {
override fun finished(description: Description?) {
super.finished(description)
Dispatchers.setMain(testDispatcher)
}
override fun starting(description: Description?) {
super.starting(description)
Dispatchers.resetMain()
testDispatcher.cleanupTestCoroutines()
}
}
Next step really depends on how you do Depedency Injection. The main point is to make sure your test codes are using coroutineRule.testDispatcher after the injection.
Finally, call runBlockingTest { } from this testDispatcher:
#Test
fun `This should pass`() = coroutineRule.testDispatcher.runBlockingTest {
//Your test code where dispatcher is injected
}

There is an open issue for this problem: https://github.com/Kotlin/kotlinx.coroutines/issues/1204
The solution is to use the CoroutineScope intead of the TestCoroutinScope until the issue is resolved, you can do by replacing
#Test
fun `signup() must be delegated to createUserWithEmailAndPassword()`() =
runBlockingTest {
with
#Test
fun `signup() must be delegated to createUserWithEmailAndPassword()`() =
runBlocking {

None of these answers quite worked for my setup due to frequent changes in the coroutines API.
This specifically works using version 1.6.0 of kotlin-coroutines-test, added as a testImplementation dependency.
#Test
fun `test my function causes flow emission`() = runTest {
// calling this function will result in my flow emitting a value
viewModel.myPublicFunction("1234")
val job = launch {
// Force my flow to update via collect invocation
viewModel.myMemberFlow.collect()
}
// immediately cancel job
job.cancel()
assertEquals("1234", viewModel.myMemberFlow.value)
}

If you have any
Channel
inside the launch, you must call to
Channel.close()
Example code:
val channel = Channel<Success<Any>>()
val flow = channel.consumeAsFlow()
launch {
channel.send(Success(Any()))
channel.close()
}

runBlockingTest deprecated since 1.6.0 and replaced with runTest.

You need to swap arch background executor with one that execute tasks synchronously. eg. For room suspend functions, live data etc.
You need the following dependency for core testing
androidTestImplementation 'androidx.arch.core:core-testing:2.1.0'
Then add the following at the top of test class
#get:Rule
val instantExecutor = InstantTaskExecutorRule()
Explanations
InstantTaskExecutorRule A JUnit Test Rule that swaps the background executor used by the
Architecture Components with a different one which executes each task
synchronously.
You can use this rule for your host side tests that use Architecture
Components

As I mentioned here about fixing runBlockingTest, maybe it could help you too.
Add this dependency if you don't have it
testImplementation "androidx.arch.core:core-testing:$versions.testCoreTesting" (2.1.0)
Then in your test class declare InstantTaskExecutorRule rule:
#get:Rule
val instantTaskExecutorRule = InstantTaskExecutorRule()

Android instrumentation test doesn't run to end when using Room #Transaction function

I'm testing with AS 3.4.1 and Emulator running Android 9.
The following test won't run, when I use a Room Dao Function annotated with #Transaction in it.
class RecurrenceManagerTest : DatabaseTest() {
#Rule
#JvmField
val instantTaskExecutorRule = InstantTaskExecutorRule()
var recurringEntryId: Long = -1
#Before
override fun setup() {
super.setup() // only initialized the db
val recurringEntry = RecurringEntry(
recurrence = Recurrence(DATE.toEpochMilli(), Recurrence.DAILY)
)
recurringEntryId = runBlocking { db.recurringEntryDao().insert(recurringEntry) }
val recurringBookEntry = BookEntry.create(
title = TITLE,
date = DATE,
value = VALUE,
isPaid = IS_PAID,
notes = NOTES,
entryType = ENTRY_TYPE,
categoryId = CATEGORY_ID,
contacts = CONTACTS,
recurringEntryId = recurringEntryId
)
runBlocking {
db.bookEntryDao().insert(recurringBookEntry) // BreakPoint #1
}
}
#Test
fun testInsertRecurrencesAndSchedule() {
var recurringEntry = runBlocking { db.recurringEntryDao().get(recurringEntryId) } // BreakPoint #2
assertThat(recurringEntry, notNullValue())
runBlocking { RecurrenceManager.insertRecurrencesAndSchedule(ApplicationProvider.getApplicationContext(), db, recurringEntry!!) }
val bookEntries = db.bookEntryDao().getBookEntries().liveDataValue()
}
}
This is the function for inserting:
#Transaction
suspend fun insert(bookEntry: BookEntry): Long {
val id = insert(bookEntry.entity)
bookEntry.embeddedContacts?.apply {
forEach {
it.id = 0
it.bookEntryId = id
}
}?.let {
insert(it)
}
return id
}
So if I'm running the test like it is (see BreakPoint #1), BreakPoint #2 won't even be called, so the test ends somewhere before, without a result.
If I'm replacing the code at BreakPoint #1 with exact the same code, the insert function has, the test runs correctly.
Does anyone have an idea what's the issue here?

You can use setTransactionExecutor to run transaction in another thread
return Room
.inMemoryDatabaseBuilder(context, MyRoomDatabase::class.java)
.setTransactionExecutor(Executors.newSingleThreadExecutor())
.build()
then while testing use runBlocking instead of runBlockingTest
#Test
fun moveItem() = runBlocking {
transactionFunction()
}

I faced the same issue and the problem was because of the InstantTaskExecutorRule, if you remove the below block of code the #Transaction should work fine with the suspend keyword
#Rule
#JvmField
val instantTaskExecutorRule = InstantTaskExecutorRule()
It seems that this rule blocks the RoomDatabase from acquiring the transaction thread. In RoomDatabase.kt execution gets blocked in the below function:
private suspend fun Executor.acquireTransactionThread(controlJob: Job): ContinuationInterceptor
Hope this helps!