get() always return null in Room database test

Issue

I am new to android and database, and studying Room Database from Google website. When I try to test the the methods in SleepDataBaseDao, sleepDao.get() always returns null. Here is the code. The insertAndGetNight() passes, but testGet() fails. I have no idea why this happens.

    @Test
        @Throws(Exception::class)
        fun insertAndGetNight() {
            val night = SleepNight()
            sleepDao.insert(night)
            val tonight = sleepDao.getTonight()
            assertEquals(tonight?.sleepQuality, -1)
        }
    @Test
        @Throws(Exception::class)
        fun testGet() {
            val night : SleepNight = SleepNight()
            val nightID : Long = night.nightId
            sleepDao.insert(night)
            val finalNight = sleepDao.get(nightID)
            assertEquals(finalNight?.nightId, nightID)
        }

    @Dao
    interface SleepDatabaseDao {
        @Insert
        fun insert(night: SleepNight)
    
        @Update
        fun update(night: SleepNight)
    
        @Query("SELECT * FROM daily_sleep_quality_table WHERE nightId=:key")
        fun get(key: Long): SleepNight
    
        @Query("DELETE FROM daily_sleep_quality_table")
        fun clear()
    
        @Query("SELECT * FROM daily_sleep_quality_table ORDER BY nightId DESC LIMIT 1")
        fun getTonight(): SleepNight?
    
        @Query("SELECT * FROM daily_sleep_quality_table ORDER BY nightId DESC")
        fun getAllNights():LiveData<List<SleepNight>>
    }

    @Entity(tableName = "daily_sleep_quality_table")
    data class SleepNight(
        @PrimaryKey(autoGenerate = true)
        var nightId: Long = 0L,
    
        @ColumnInfo(name = "start_time_milli")
        var startTimeMilli: Long = System.currentTimeMillis(),
    
        @ColumnInfo(name = "end_time_milli")
        var endTimeMilli: Long = startTimeMilli,
    
        @ColumnInfo(name = "quality_rating")
        var sleepQuality: Int = -1
    )

Thanks for any help!

Solution

You have default id 0 in your SleepNight class but autoGenerate is true. I think that when you are creating new SleepNight your nightID is 0, but ids in database table starting from 1 and dao cant find it.

Answered By - Mirek Hýbler