Android Instrumented Unit Test With Room Using In Memory Database And LiveData

May 14, 2018

Use Room.inMemoryDatabaseBuilder To Avoid Overwrite Database With Test Data

NOTE: Refer to Android Instrumented Unit Test With Hamcrest if you are unfamiliar with it.

Create LiveDataTestUtil.getValue (Source) to retrive value from LiveData in Unit Test.

object LiveDataTestUtil {
    // @Throws(InterruptedException::class)
    fun <T> getValue(liveData: LiveData<T>): T {
        val data = arrayOfNulls<Any>(1)
        val latch = CountDownLatch(1)
        val observer = object : Observer<T> {
            override fun onChanged(o: T?) {
                data[0] = o
                latch.countDown()
                liveData.removeObserver(this)
            }
        }
        liveData.observeForever(observer)
        latch.await(2, TimeUnit.SECONDS)

        return data[0] as T
    }
}

Sample DatabaseTest to show

Room In Memory Database for Unit Testing
Unit Test with LiveData
Unit Test with Room DAO Insert

import org.hamcrest.CoreMatchers.`is` as Is

@RunWith(AndroidJUnit4::class)
class DatabaseTest {
    // this is RoomDatabase
    private lateinit var db: AppDatabase

    @Before
    fun init() {
        db = Room.inMemoryDatabaseBuilder(InstrumentationRegistry.getContext(),
                AppDatabase::class.java).build()
    }

    @After
    fun closeDb() {
        db.close()
    }

    @Test
    fun testIfEmpty() {
        val liveData = db.photoPinDao().fetchAll()
        var items = LiveDataTestUtil.getValue(liveData)
        assertThat(items.size, Is(0))
    }

    @Test
    fun testInsertValue() {
        var item = PhotoPin(name="test")
        assertThat(item.name, Is("test"))

        // could create Kotlin extension to simplified this code
        db.beginTransaction()
        db.photoPinDao().insert(item)
        db.setTransactionSuccessful()
        db.endTransaction()

        var items = getValue(db.photoPinDao().fetchAll())
        assertThat(items.size, Is(1))

        item = items[0]
        assertThat(item.name, Is("test"))
    }    
}