Exercise: Test UserDetailsRepository
In a previous exercise, we implemented a UserDetailsRepository class. Here is a possible implementation:
class UserDetailsRepository(
private val client: UserDataClient,
private val userDatabase: UserDetailsDatabase,
private val backgroundScope: CoroutineScope,
) {
suspend fun getUserDetails(): UserDetails =
coroutineScope {
val stored = userDatabase.load()
if (stored != null) {
return@coroutineScope stored
}
val name = async { client.getName() }
val friends = async { client.getFriends() }
val profile = async { client.getProfile() }
val details = UserDetails(
name = name.await(),
friends = friends.await(),
profile = profile.await(),
)
backgroundScope.launch { userDatabase.save(details) }
details
}
}
Your task is to implement a single unit test, that verifies the following behavior:
- should fetch name, friends, and profile asynchronously,
- should return fetched details,
- should save details to the database asynchronously,
- should load details from the database if they are already there.
Here is your starting code to modify:
Starting code:
@Test
fun `should fetch details asynchronously`() = runTest {
// given
val client = object : UserDataClient {
override suspend fun getName(): String {
// TODO
return "Ben"
}
override suspend fun getFriends(): List<Friend> {
// TODO
return listOf(Friend("friend-id-1"))
}
override suspend fun getProfile(): Profile {
// TODO
return Profile("Example description")
}
}
var savedDetails: UserDetails? = null
val database = object : UserDetailsDatabase {
override suspend fun load(): UserDetails? {
// TODO
return savedDetails
}
override suspend fun save(user: UserDetails) {
// TODO
savedDetails = user
}
}
val repo: UserDetailsRepository = TODO()
// when
val details = repo.getUserDetails()
// then data are fetched asynchronously
// TODO
// when all children are finished
// TODO
// then data are saved to the database
// TODO
// when getting details again
// TODO
// then data are loaded from the database
// TODO
}
This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in coroutines/test/TestUserDetailsRepository.kt. You can find there starting code.
Once you are done with the exercise, you can check your solution here.
Playground
import kotlinx.coroutines.*
import kotlinx.coroutines.test.currentTime
import kotlinx.coroutines.test.runTest
import org.junit.Test
import kotlin.test.assertEquals
class UserDetailsRepository(
private val client: UserDataClient,
private val userDatabase: UserDetailsDatabase,
private val backgroundScope: CoroutineScope,
) {
suspend fun getUserDetails(): UserDetails = coroutineScope {
val stored = userDatabase.load()
if (stored != null) {
return@coroutineScope stored
}
val name = async { client.getName() }
val friends = async { client.getFriends() }
val profile = async { client.getProfile() }
val details = UserDetails(
name = name.await(),
friends = friends.await(),
profile = profile.await(),
)
backgroundScope.launch { userDatabase.save(details) }
details
}
}
interface UserDataClient {
suspend fun getName(): String
suspend fun getFriends(): List<Friend>
suspend fun getProfile(): Profile
}
interface UserDetailsDatabase {
suspend fun load(): UserDetails?
suspend fun save(user: UserDetails)
}
data class UserDetails(
val name: String,
val friends: List<Friend>,
val profile: Profile
)
data class Friend(val id: String)
data class Profile(val description: String)
@Suppress("FunctionName")
class UserDetailsRepositoryTest {
@Test
fun `should fetch details asynchronously`() = runTest {
// given
val client = object : UserDataClient {
override suspend fun getName(): String {
// TODO
return "Ben"
}
override suspend fun getFriends(): List<Friend> {
// TODO
return listOf(Friend("friend-id-1"))
}
override suspend fun getProfile(): Profile {
// TODO
return Profile("Example description")
}
}
var savedDetails: UserDetails? = null
val database = object : UserDetailsDatabase {
override suspend fun load(): UserDetails? {
// TODO
return savedDetails
}
override suspend fun save(user: UserDetails) {
// TODO
savedDetails = user
}
}
val repo: UserDetailsRepository = TODO()
// when
val details = repo.getUserDetails()
// then data are fetched asynchronously
// TODO
// when all children are finished
// TODO
// then data are saved to the database
// TODO
// when getting details again
// TODO
// then data are loaded from the database
// TODO
}
}
