Room DAO with Kotlin Coroutines and Flow 测试方法

Question

我正尝试在我的 Room Dao 中从 LiveData 迁移到 Flow。应用程序运行良好，但我在测试行为方面遇到问题。当我运行测试开始时运行不确定。我也尝试使用 kotlinx.coroutines.test 运行BlockingTest，但我对 "This job has not finished yet" 有疑问，比如 here。有人可以指出正确的方向如何测试我的 CoresDao 的行为吗？

@Dao
interface CoresDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insertCores(cores: List<Core>)

    @Transaction
    suspend fun replaceCoresData(cores: List<Core>) {
        deleteAllCores()
        insertCores(cores)
    }

    @Query("SELECT * FROM cores_table")
    fun getAllCores(): Flow<List<Core>>

    @Query("DELETE FROM cores_table")
    suspend fun deleteAllCores()
}

@RunWith(AndroidJUnit4::class)
class CoresDaoTest {

    private lateinit var database: SpaceDatabase
    private lateinit var coresDao: CoresDao

    private val testDispatcher = TestCoroutineDispatcher()

    private val testCoresList = listOf(core2, core3, core1)

    @get:Rule
    var instantTaskExecutorRule = InstantTaskExecutorRule()

    @Before
    fun setup() {
        Dispatchers.setMain(testDispatcher)

        val context = InstrumentationRegistry.getInstrumentation().targetContext
        database = Room.inMemoryDatabaseBuilder(context, SpaceDatabase::class.java).build()
        coresDao = database.coresDao()
    }

    @After
    fun cleanup() {
        database.close()

        Dispatchers.resetMain()
        testDispatcher.cleanupTestCoroutines()
    }

    @Test
    fun testGetAllCores(): Unit = runBlocking {
        withContext(Dispatchers.Main) {
            runBlocking { coresDao.insertCores(testCoresList) }

            val coresList = mutableListOf<Core>()
            coresDao.getAllCores().collect { cores -> coresList.addAll(cores) }

            assertThat(coresList.size, equalTo(testCoresList.size))
        }
    }
}

Answer 1

由于您已经在使用 TestCoroutineDispatcher，因此在您的示例中使用 runBlockingTest 不会执行任何操作。您必须 cancel 收集后 Flow 或 scope 在其中启动 Flow

编辑：可以找到此类规则的示例 here

Answer 2

事实证明我没有正确处理 Flow 收集和取消，这可能是问题的原因。下面是有效的代码。可以找到更复杂的示例 here.

@RunWith(AndroidJUnit4::class)
class CoresDaoTest {

    private lateinit var database: SpaceDatabase
    private lateinit var coresDao: CoresDao

    private val testDispatcher = TestCoroutineDispatcher()

    private val testCoresList = listOf(core2, core3, core1)

    @get:Rule
    var instantTaskExecutorRule = InstantTaskExecutorRule()

    @Before
    fun setup() {
        Dispatchers.setMain(testDispatcher)

        val context = InstrumentationRegistry.getInstrumentation().targetContext
        database = Room
            .inMemoryDatabaseBuilder(context, SpaceDatabase::class.java)
            .setTransactionExecutor(Executors.newSingleThreadExecutor())
            .build()
        coresDao = database.coresDao()
    }

    @After
    fun cleanup() {
        database.close()

        Dispatchers.resetMain()
        testDispatcher.cleanupTestCoroutines()
    }

    @Test
    fun testInsertAndGetAllCores() = runBlocking {
        coresDao.insertCores(testCoresList)

        val latch = CountDownLatch(1)
        val job = launch(Dispatchers.IO) {
            coresDao.getAllCores().collect { cores ->
                assertThat(cores.size, equalTo(testCoresList.size))
                latch.countDown()
            }
        }

        latch.await()
        job.cancel()
    }

Answer 3

为了测试 Flow，我找到的最好的 API 是 .take(n).toList()。您可以使用 runBlockingTest 而不需要使用 withContext 将执行移至另一个线程。

您可以在此处找到其工作原理的示例： https://github.com/manuelvicnt/MathCoroutinesFlow/blob/master/app/src/test/java/com/manuelvicnt/coroutinesflow/fibonacci/impl/NeverEndingFibonacciProducerTest.kt#L38

Room DAO with Kotlin Coroutines and Flow 测试方法

Test methods of Room DAO with Kotlin Coroutines and Flow

android

unit-testing

android-room

kotlin-coroutines

kotlinx.coroutines.flow