如何测试返回DataSource.Factory的Dao方法？

Question

After shifting from SqliteOpenHelper to room in my app, I've trying to write tests for the DAO class.

My DAO looks something like this:

    @Query("SELECT * FROM cards")
    fun getAllCards(): List<CardData>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insertCard(vararg cardData: CardData): List<Long>

    @Query("SELECT * FROM cards ORDER BY isRead ASC, id DESC")
    fun getItemList(): DataSource.Factory<Int, CardData>

    @Query("SELECT * FROM cards where instr(title, :query) > 0 ORDER BY isRead ASC, id DESC")
    fun getItemList(query: String): DataSource.Factory<Int, CardData>

    @Query("UPDATE cards set isRead = 1 where title = :title")
    fun markRead(title: String): Int

While writing test for getAllCards , insertCard and markRead is trivial, I am still not sure how do I test the apis which return DataSource.Factory , ie getItemList apis.

After searching on internet, I couldn't find anything related to this.

Can someone please help.

Answer 1

this is how I did:

val factory = dao.getItemList()
val list = (factory.create() as LimitOffsetDataSource).loadRange(0, 10)

Quoting CommonsWare

If you use paging with Room and have a @Dao method return a DataSource.Factory, the generated code uses an internal class named LimitOffsetDataSource to perform the SQLite operations and fulfill the PositionalDataSource contract.

source: https://commonsware.com/AndroidArch/previews/paging-beyond-room#head206