Exercise: Flow testing
Test the observeAppointments function from the ObserveAppointmentsUseCase class. Starting code:
class ObserveAppointmentsUseCase(
private val appointmentRepository: AppointmentRepository
) {
fun observeAppointments(): Flow<List<Appointment>> =
appointmentRepository
.observeAppointments()
.filterIsInstance<AppointmentUpdate>()
.map { it.appointments }
.distinctUntilChanged()
.retry { it is ApiException && it.code in 500..599 }
}
interface AppointmentRepository {
fun observeAppointments(): Flow<AppointmentEvent>
}
sealed class AppointmentEvent
data class AppointmentUpdate(
val appointments: List<Appointment>
) : AppointmentEvent()
data object AppointmentConfirmed : AppointmentEvent()
data class Appointment(val title: String, val time: Instant)
data class ApiException(val code: Int) : Throwable()
You should test the following cases:
- should receive only appointment lists from appointment updates
- should not receive non-distinct values
- should retry exceptions of type
ApiExceptionwith code 5XX
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/flow/ObserveAppointmentsUseCase.kt. You can find there starting code.
Playground
import kotlinx.coroutines.flow.*
import java.time.Instant
class ObserveAppointmentsUseCase(
private val appointmentRepository: AppointmentRepository
) {
fun observeAppointments(): Flow<List<Appointment>> =
appointmentRepository
.observeAppointments()
.filterIsInstance<AppointmentUpdate>()
.map { it.appointments }
.distinctUntilChanged()
.retry { it is ApiException && it.code in 500..599 }
}
interface AppointmentRepository {
fun observeAppointments(): Flow<AppointmentEvent>
}
sealed class AppointmentEvent
data class AppointmentUpdate(
val appointments: List<Appointment>
) : AppointmentEvent()
data object AppointmentConfirmed : AppointmentEvent()
data class Appointment(val title: String, val time: Instant)
data class ApiException(val code: Int) : Throwable()
