UserDaoTest.kt

@RunWith(AndroidJUnit4::class)
class UserDaoTest {

    lateinit var userDao: UserDao
    lateinit var database: AppDatabase

    @Before
    fun setup() {
        val context = InstrumentationRegistry.getTargetContext()
        database = Room.inMemoryDatabaseBuilder(context, AppDatabase::class.java).build()
        userDao = database.userDao()
    }

    @After
    fun tearDown() {
        database.close()
    }

    @Test
    fun testInsertedAndRetrievedUsersMatch() {
        val users = listOf(User(1, "Name", 100, "url"), User())
        userDao.insertAll(users)

        val allUsers = userDao.getUsers(1)
        assertEquals(users, allUsers)
    }

    @Test
    fun testUsersOrderedByCorrectly() {
        val users = listOf(
                User(1, "Name", 100, "url"),
                User(2, "Name2", 500, "url"),
                User(3, "Name3", 300, "url"))
        userDao.insertAll(users)

        val allUsers = userDao.getUsers(1)
        val expectedUsers = users.sortedByDescending { it.reputation }
        assertEquals(expectedUsers, allUsers)
    }

    @Test
    fun testConflictingInsertsReplaceUsers() {
        val users = listOf(
                User(1, "Name", 100, "url"),
                User(2, "Name2", 500, "url"),
                User(3, "Name3", 300, "url"))

        val users2 = listOf(
                User(1, "Name", 1000, "url"),
                User(2, "Name2", 700, "url"),
                User(4, "Name3", 5500, "url"))
        userDao.insertAll(users)
        userDao.insertAll(users2)

        val allUsers = userDao.getUsers(1)
        val expectedUsers = listOf(
                User(4, "Name3", 5500, "url"),
                User(1, "Name", 1000, "url"),
                User(2, "Name2", 700, "url"),
                User(3, "Name3", 300, "url"))

        assertEquals(expectedUsers, allUsers)
    }

    @Test
    fun testLimitUsersPerPage_FirstPageOnly30Items() {
        val users = (1..40L).map { User(it, "Name $it", it *100, "url") }

        userDao.insertAll(users)

        val retrievedUsers = userDao.getUsers(1)
        assertEquals(30, retrievedUsers.size)
    }

    @Test
    fun testRequestSecondPage_LimitUsersPerPage_showOnlyRemainingItems() {
        val users = (1..40L).map { User(it, "Name $it", it *100, "url") }

        userDao.insertAll(users)

        val retrievedUsers = userDao.getUsers(2)
        assertEquals(10, retrievedUsers.size)
    }
}