Android 单元测试从方法内部的房间返回的LiveData

我有一个方法，它从房间的DAO层获取LiveData对象，然后对LiveData对象执行一些操作

每当我尝试执行

dataStorage.getAllSections（）

时，它都会返回一个LiveData对象，并且该值始终为null。（我的数据库已预填充）

我已经为LiveData声明了JUnit规则

@get:Rule
val rule = InstantTaskExecutorRule()

在我的实际类中，如果我创建一个扩展函数来像这样等待LiveData

private fun <T> LiveData<T>.blockingObserve(): T? {
    var value: T? = null
    val latch = CountDownLatch(1)

    val observer = Observer<T> { t ->
        value = t
        latch.countDown()
    }

    observeForever(observer)

    latch.await(2, TimeUnit.SECONDS)
    return value
}

单元测试运行良好。我没有得到空指针异常。 我甚至尝试过使用

runBlocking

运行测试，但这也没有帮助

This is my method I am trying to test: 

@VisibleForTesting
fun buildDataFromDB(): LiveData<List<SectionModel>> {

    Logger.d(TAG, "Building data from DB")

    val sections = dataStorage.getAllSections() 
    // sections.value is always null even though my DB is populated 
    sections.value?.forEach { section ->
        // Do something 
        }
    }

    Logger.d(TAG, "Building data from DB completed")

    return sections
}

This is my method I am trying to test: 

@VisibleForTesting
fun buildDataFromDB(): LiveData<List<SectionModel>> {

    Logger.d(TAG, "Building data from DB")

    val sections = dataStorage.getAllSections() 
    // sections.value is always null even though my DB is populated 
    sections.value?.forEach { section ->
        // Do something 
        }
    }

    Logger.d(TAG, "Building data from DB completed")

    return sections
}

@Test
fun test_buildDataFromDb() = runBlocking {
    val result = appDataProvider.buildDataFromDB().blockingObserve()
    // asserts
}