Develop Reference

How I can mock response of Apollo Android

I'm trying to mock response to my query but I can't because the builder needed and doesn't know how to pass operations?
Basicly I have network class like this :
class NetworkService #Inject constructor(
private val apolloClient: ApolloClient
) {
suspend fun <D : Operation.Data, T, V : Operation.Variables> suspendedQuery(
query: Query<D, T, V>,
cachePolicy: HttpCachePolicy.Policy = HttpCachePolicy.NETWORK_FIRST
): Resource<Response<T>> {
val response = try {
apolloClient.query(query)
.toBuilder().httpCachePolicy(cachePolicy)
.build()
.await()
} catch (e: ApolloException) {
return Resource.error(e.localizedMessage)
}
return if (response.hasErrors()) {
Resource.error(response.errors.toString())
} else {
Resource.success(response)
}
}
}
and I want to mock the response returned from this function like this
I successed when I'm returning an error
val expectedResponse = Resource.error<Response<MyQuery.Data>>("ERROR")
But I have problem to mocking the resposne here:
val expectedResponse = Resource.success<Response<MyQuery.Data>>(Response("Response.builder(Operation<>)"))
I want to know How to build the inside the quote "Response.builder(Operation<>)"?

It would appear that this is a long running problem according to the apollo-android issues list. I can see that you've asked a similar question there also.
I found this issue which looks to be resolving this problem in the not too distant future. It was supposed to be this month but now looks like next.
So think this means that you're only solution right now is to use mock web server, and have it return a sample response to the client. This is how we have implemented our tests currently.

How do I test a Kotlin suspend call in Android with MockK?

I'm trying my hand at TDD with an Android app. I'm writing it in Kotlin, and because of that I've turned to MockK for testing, but there's one thing (for now) that I haven't been able to find out how to do: test a suspend call.
I wrote a test for a LiveData value in a ViewModel, and made it work. However, when I added coroutines to the mix, I started getting the "Method getMainLooper not mocked" message.
Here's my code:
ToDoListViewModelTest.kt
class ToDoListViewModelTest {
#get:Rule
var instantExecutorRule = InstantTaskExecutorRule()
#MockK
private lateinit var toDoListLiveDataObserver: Observer<List<ToDoItem>>
#MockK
private lateinit var getToDoItemsUseCase: GetToDoItemsUseCase
#Before
fun setUp() {
MockKAnnotations.init(this)
every { toDoListLiveDataObserver.onChanged(any()) } answers { nothing }
}
#Test
fun toDoList_listItems_noItems() = runBlocking {
coEvery { getToDoItemsUseCase() } coAnswers { emptyList<ToDoItem>() }
val toDoListViewModel = ToDoListViewModel(getToDoItemsUseCase)
toDoListViewModel.toDoItemList.observeForever(toDoListLiveDataObserver)
toDoListViewModel.updateItemList()
assertEquals(0, toDoListViewModel.toDoItemList.value?.size)
}
}
ToDoListViewModel.kt
class ToDoListViewModel(private val getToDoItemsUseCase: GetToDoItemsUseCase) : ViewModel() {
private val _toDoItemList: MutableLiveData<List<ToDoItem>> = MutableLiveData()
val toDoItemList : LiveData<List<ToDoItem>> = _toDoItemList
fun updateItemList() {
viewModelScope.launch(Dispatchers.IO) {
_toDoItemList.value = getToDoItemsUseCase()
}
}
}
GetToDoItemsUseCase.kt
class GetToDoItemsUseCase {
suspend operator fun invoke(): List<ToDoItem> {
return listOf()
}
}
Things I've tried:
Adding "#RunWith(BlockJUnit4ClassRunner::class)": No change
Adding "testOptions { unitTests.returnDefaultValues = true }" to the Gradle file: The Looper error goes away, but the value coming from the LiveData is null, instead of the empty list specified in the "coEvery" call.
Calling "Dispatchers.setMain(newSingleThreadContext("UI Thread"))": Same as previous case, getting null from LiveData.
I'm not very experienced with testing, and I've run out of options. I feel I definitely need some help from the community ;)
Also, if for some reason my setup isn't the right one (should use something other than MockK, or some other testing framework...), please comment on that too. I still have much to learn regarding this.

Use postValue _toDoItemList.postValue(getToDoItemsUseCase())
Based on the documentation:
setValue():
Sets the value. If there are active observers, the value will be
dispatched to them. This method must be called from the main thread.
postValue():
Posts a task to a main thread to set the given value. If you called
this method multiple times before a main thread executed a posted
task, only the last value would be dispatched.

How to properly separate Realm from the rest of the app?

In my app I am trying to use MVVM with repositories databases and all that. I like to keep all my external dependencies and such separate and compartmentalized into their own files/modules so that they can easily be replaced or swapped out.
With Realm I could make this work really well by using unmanaged objects. I can have a RealmHelper class for example which just opens a realm instance, queries or performs some transaction and then closes the realm and returns an object.
So how can I accomplish something similar with managed objects? The problem is in this case that you have to know when to close the realm. The obvious solution here I think is to let the database know when you are done with it, but this seems like a tedious and unoptimized solution. Is there another better way?

So I have attempted to come up with a solution to this myself. I haven't tested it very well yet but my idea is basically to modify the LiveRealmResults file from the official example to let the caller (RealmHelper for example) know when it changes states between inactive and active. When it is active the caller will open the realm and pass in the results. When it changes to inactive the caller will close the realm. This is what my LiveRealmResults looks like:
#MainThread
class LiveRealmResults<T : RealmModel>(
private val getResults: () -> RealmResults<T>,
private val closeRealm: () -> Unit
) : LiveData<List<T>>() {
private var results: RealmResults<T>? = null
private val listener = OrderedRealmCollectionChangeListener<RealmResults<T>> {
results, _ ->
this#LiveRealmResults.value = results
}
override fun onActive() {
super.onActive()
results = getResults()
if (results?.isValid == true) {
results?.addChangeListener(listener)
}
if (results?.isLoaded == true) {
value = results
}
}
override fun onInactive() {
super.onInactive()
if (results?.isValid == true) {
results?.removeChangeListener(listener)
}
removeObserver()
}
}
It will be used like so:
class RealmHelper() {
fun getObjects(): LiveData<List<Objects>> {
var realm: Realm? = null
return LiveRealmResults<Objects>(getResults = {
realm = Realm.getDefaultInstance()
realm!!.where<Objects>().findAll()
}, removeObserver = {
realm?.close()
})
}
}
This method at least allows me to keep all realm logic in the RealmHelper, only exposing LiveData and not RealmResults. Whenever the LiveData is inactive the Realm is closed. In my example I'm returning RealmObject but I'm fine converting from RealmObject to normal object so I'm am not concerned with that part for this example.

Unit testing coroutines on UI thread

I'm using coroutines to do an asynchronous call on pull to refresh like so:
class DataFragment : Fragment(), SwipeRefreshLayout.OnRefreshListener {
// other functions here
override fun onRefresh() {
loadDataAsync()
}
private fun loadDataAsync() = async(UI) {
swipeRefreshLayout?.isRefreshing = true
progressLayout?.showContent()
val data = async(CommonPool) {
service?.getData() // suspending function
}.await()
when {
data == null -> showError()
data.isEmpty() -> progressLayout?.showEmpty(null, parentActivity?.getString(R.string.no_data), null)
else -> {
dataAdapter?.updateData(data)
dataAdapter?.notifyDataSetChanged()
progressLayout?.showContent()
}
}
swipeRefreshLayout?.isRefreshing = false
}
}
Everything here works fine when I actually put it on a device. My error, empty, and data states are all handled well and the performance is good. However, I'm also trying to unit test it with Spek. My Spek test looks like this:
#RunWith(JUnitPlatform::class)
class DataFragmentTest : Spek({
describe("The DataFragment") {
var uut: DataFragment? = null
beforeEachTest {
uut = DataFragment()
}
// test other functions
describe("when onRefresh") {
beforeEachTest {
uut?.swipeRefreshLayout = mock()
uut?.onRefresh()
}
it("sets swipeRefreshLayout.isRefreshing to true") {
verify(uut?.swipeRefreshLayout)?.isRefreshing = true // says no interaction with mock
}
}
}
}
The test is failing because it says that there was no interaction with the uut?.swipeRefreshLayout mock. After some experimenting, it seems this is because I'm using the UI context via async(UI). If I make it just be a regular async, I can get the test to pass but then the app crashes because I'm modifying views outside of the UI thread.
Any ideas why this might be occurring? Also, if anyone has any better suggestions for doing this which will make it more testable, I'm all ears.
Thanks.
EDIT: Forgot to mention that I also tried wrapping the verify and the uut?.onRefresh() in a runBlocking, but I still had no success.

If you want to make things clean and consider using MVP architecture in the future you should understand that CourutineContext is external dependency, that should be injected via DI, or passed to your presenter. More details on topic.
The answer for your question is simple, you should use only Unconfined CourutineContext for your tests. (more)
To make things simple create an object e.g. Injection with:
package com.example
object Injection {
val uiContext : CourutineContext = UI
val bgContext : CourutineContext = CommonPool
}
and in test package create absolutely the same object but change to:
package com.example
object Injection {
val uiContext : CourutineContext = Unconfined
val bgContext : CourutineContext = Unconfined
}
and inside your class it will be something like:
val data = async(Injection.bgContext) {service?.getData()}.await()

How to pass null to an Observable with nullable type in RxJava 2 and Kotlin

I initialize my variable like this:-
val user: BehaviorSubject<User?> user = BehaviorSubject.create()
But I can't do this. IDE throws an error:-
user.onNext(null)
And doing this, IDE says u will never be null:-
user.filter( u -> u!=null)

As Guenhter explained, this is not possible. However, instead of proposing the null-object pattern, I'd recommend an implementation of the Optional type:
data class Optional<T>(val value: T?)
fun <T> T?.asOptional() = Optional(this)
This makes your intent much clearer, and you can use a destructuring declaration in your functions:
Observable.just(Optional("Test"))
.map { (text: String?) -> text?.substring(1)?.asOptional() }
.subscribe()
Using the null-object pattern here can cause more bugs than it solves.

If you use rxkotlin/rxjava 2.0 (I assume so) than the answer is: you can't. The reason is explained here.
This is a break of the interface. Have a look at the Observable Interface
public interface Observer<T> {
/** ... */
void onSubscribe(#NonNull Disposable d);
/** ... */
void onNext(#NonNull T t);
/** ... */
void onError(#NonNull Throwable e);
/** ... */
void onSubscribe(#NonNull Disposable d);
/** ... */
void onNext(#NonNull T t);
/** ... */
void onError(#NonNull Throwable e);
...
The #NonNull will be considered by the Kotlin compiler and therefore you CAN'T pass null.
Even if you could, the onNext would immediately throw an error:
#Override
public void onNext(T t) {
if (t == null) {
onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
return;
}
...
}
If you really need such a thing as null you have to fake it. e.g. by creating a static object of User which represents your null-element.
e.g.
data class User(val username, val password) {
companion object {
val NULL_USER = User("", "")
}
}
...
val user = BehaviorSubject.create<User>()
...
user.onNext(User.NULL_USER)
...
user.filter { it !== User.NULL_USER }
But if is somehow possible, try to avoid the null concept and maybe think of another solution where this isn't needed.

Thank you very much for all your answers but I ultimately went with this solution:-
class UserEnvelope(val user:User?) {}
And using this in the observables.
This best suited my requirements.
I am new to Kotlin so I don't know how to use Optionals. But from what I understand, I would have to typecast it to User type everytime I need to observe the values right?

To implement the solution mentioned in the nhaarman's answer, you can use the util class Optional (doc) from the Android SDK which was added in API level 24.
If your app's minSdkVersion less than 24 then you still need to implement it by yourself.

Since RxJava 2 does not support null values, there are some other acceptable solutions you can use:
Work with a custom or third party wrapper library of Optionals like some of the posted answers suggest. When I got rid of Java in favour of Kotlin, Optionals went away in the same package since Kotlin per se supports nullability as part of its type System. Just by this change the code was much more clearer, and I personally don't want to get Optionals back in my code as long as I can avoid them.
Emit Any class instances with your subject type. For example you could create an Empty.INSTANCE enum class which would emulate the null value and then filter by the enum class.
The last one is the one I use and prefer being a variant of the previous solution and is based on specialisations. Our friends of JetBrains always emphasise that classes are very cheap in Kotlin, so this would be a quick example to distinguish logged users and not logged ones:
abstract class SessionUser
sealed class LoggedUser(val username: String, val password: String) : SessionUser()
sealed class LogoutUser : SessionUser()
private val user = BehaviorSubject.create<SessionUser>()
private val loggedUser =
user.filter { it is LoggedUser }.cast(LoggedUser::class.java)
fun login(username: String, password: String) {
user.onNext(LoggedUser(username, password))
}
fun logout() {
user.onNext(LogoutUser())
}

I've taken an approach similar to Optional<User> and UserEnvelope. I make a simple User class and a ReifiedUser class that inherits from it. The User class has a companion object that has a NONE instance. The BehaviorSubject is instantiated with the User.NONE instance. It looks something like this:
open class User {
companion object {
val NONE = User()
}
}
class ReifiedUser(
#field:JsonProperty(J.FirstName) val firstName: String,
#field:JsonProperty(J.LastName) val lastName: String
) : User()
My BehaviorSubject is instantiated like this:
val activeUser: BehaviorSubject<User> = BehaviorSubject.createDefault(User.NONE)
And wherever I need to use activeUser I either flatMap it to Observable.empty() if it's NONE or just figure out what it is and what to do in the subscriber.
I don't like mixing java Optional with kotlin nullable because mixing map and let gets really confusing and ugly. This way it's very obvious what's going on.

I think it makes more sense to write a container class such as Result. An example of that would be
data class Result<T>(value: T?, error: Throwable?)
Usage
Observable.create { observer ->
upstreamService.listen(object: UpstreamListener {
onSuccess(data: User) {
observer.onSuccess(Result(data))
}
onError(exception: Throwable) {
observer.onSuccess(Result(null, exception))
}
}
}