Test RxJava2 Flowable Query Room

Question

I've been trying to write unit tests for my Room database, which I've done in the past when I have queries return a list and I create a database that allows main thread queries, but now that I'm trying to test with RxJava values I have no luck.

Here is my DAO code:

@Dao
interface AccountDAO {
    @Query("SELECT * FROM account")
    fun getAll(): Flowable<List<Account>>

    @Insert
    fun insert(accounts: List<Account>): List<Long>

    //...
}

And here is my database testing code, where I've tried a few things to get it to pass:

@RunWith(AndroidJUnit4::class)
class CCDatabaseTest {
    //...

    @JvmField @Rule val mainActivity = ActivityTestRule<MainActivity>(MainActivity::class.java)

    @Before
    fun setUp() {
        val context = mainActivity.activity
        database = Room.inMemoryDatabaseBuilder(context, CCDatabase::class.java).allowMainThreadQueries().build()
        accountDao = database.accountDao()
        transactionDao = database.transactionDao()
    }

    //...

    @Test
    fun testWriteReadAccount() {
        val testAccount = Account(TEST_ACCOUNT_NAME, TEST_ACCOUNT_BALANCE)

        val ids = accountDao.insert(listOf(testAccount))
        assertEquals(1, ids.size)

        val accountsFlowable = accountDao.getAll()
        val testSubscriber = TestSubscriber<List<Account>>()
        accountsFlowable.subscribe(testSubscriber)

        testSubscriber.assertNoErrors()
        // Fails: testSubscriber.assertValueCount(1)
        // Fails: testSubscriber.assertValue(listOf(testAccount))
        // Fails: testSubscriber.assertResult(listOf(testAccount))
    }

    //...
}

If anyone would actually like to see or test run the code, please check out the app-refresh module of this repository: https://github.com/adammc331/cashcaretaker

DAO: https://github.com/AdamMc331/CashCaretaker/blob/develop/app-refresh/src/main/java/com/adammcneilly/cashcaretaker/daos/AccountDAO.kt

Test class: https://github.com/AdamMc331/CashCaretaker/blob/develop/app-refresh/src/androidTest/java/com/adammcneilly/cashcaretaker/data/CCDatabaseTest.kt

Answer 1

As part of my search to answer this, I commented on a Medium post by Florina Muntenescu and she responded with the answer.

I needed to include the InstantTaskExecutorRule in my test class. This replaces the background task executor with one that runs everything synchronously. In order to use this, I added the following line to my module's build.gradle file, note that while I had to exclude certain modules (I got a support lib discrepancy between app and test app) you may not:

androidTestCompile ("android.arch.core:core-testing:$roomLibraryVersion") {
    exclude module: 'support-compat'
    exclude module: 'support-annotations'
    exclude module: 'support-core-utils'
}

Now, with that added, my test class looks like this:

@RunWith(AndroidJUnit4::class)
class CCDatabaseTest {
    // ...

    @JvmField @Rule val instantTaskExecutorRule = InstantTaskExecutorRule()
    @JvmField @Rule val mainActivity = ActivityTestRule<MainActivity>(MainActivity::class.java)

    @Before
    fun setUp() {
        val context = mainActivity.activity
        database = Room.inMemoryDatabaseBuilder(context, CCDatabase::class.java).allowMainThreadQueries().build()
        accountDao = database.accountDao()
    }

    // ...

    @Test
    fun testWriteReadAccount() {
        val testAccount = Account(TEST_ACCOUNT_NAME, TEST_ACCOUNT_BALANCE)

        val ids = accountDao.insert(listOf(testAccount))
        assertEquals(1, ids.size)

        accountDao.getAll()
                .test()
                .assertValue(listOf(testAccount))
    }

    // ...
}