Test with JUnit an request - junit

Question

I wanna to test an request with JUnit with an request like this but RxUtils.applySchedulersAndErrorMapper() return null. Is any possibilities to test that?
override fun onContinueClicked(phoneNumber: String) {
mView.showLoading()
mUserService.checkUserApprovedStatus(phoneNumber)
.compose(RxUtils.applySchedulersAndErrorMapper())
.subscribe({ response ->
//Success
}, { error ->
//Error
})
}
here is where I setup the presenter and mUserService for presenter
#Mock
private PhoneContract.View view;
#Mock
private UserService userService;
#Before
public void setup() {
presenter = new PhonePresenter(this.view);
presenter.mUserService = userService;
}
here is the test method
#Test
public void onContinueClicked_SendJustNumbers() {
String phoneNumber = "(01234567890)";
// when
presenter.onContinueClicked(phoneNumber);
// then
verify(view, times(1)).showLoading();
}
and here is the RXUtils class:
class RxUtils {
companion object {
#SuppressLint("CheckResult")
fun <E> applySchedulersAndErrorMapper(): ObservableTransformer<E, E> {
return ObservableTransformer { o ->
o.flatMap(Function<E, ObservableSource<E>> { element ->
val genericResponse = element as GenericResponse<*>
#Suppress("UNCHECKED_CAST")
return#Function Observable.just(genericResponse as E)
}).onErrorResumeNext(Function<Throwable, ObservableSource<E>> { t ->
if (t is ApiException) {
return#Function Observable.error(t)
}
var genericResponse: GenericResponse<*>? = null
return#Function Observable.error(ApiException(t.message ?: "", genericResponse?.result ?: Result()))
})
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
}
}
}
}
Here is the stacktrace where I receive null for RxUtils.applySchedulersAndErrorMapper()
java.lang.NullPointerException

Answer 1

If it relates to the SDK, it probably won't work in a unit test. You didn't include your imports, so it's impossible to tell at a glance, but I know from experience that you can't use this in a unit test
AndroidSchedulers.mainThread()
You need to replace that with, say, Schedulers.trampoline()
Example of how to set a custom scheduler for testing
Note, this is only an example, and there are other valid solutions.
class RxUtils {
companion object {
// add this
#VisibleForTesting var mainScheduler = AndroidSchedulers.mainThread()
#VisibleForTesting var ioScheduler = Schedulers.io()
#SuppressLint("CheckResult")
fun <E> applySchedulersAndErrorMapper(): ObservableTransformer<E, E> {
return ObservableTransformer { o ->
o.flatMap(Function<E, ObservableSource<E>> { element ->
val genericResponse = element as GenericResponse<*>
#Suppress("UNCHECKED_CAST")
return#Function Observable.just(genericResponse as E)
}).onErrorResumeNext(Function<Throwable, ObservableSource<E>> { t ->
if (t is ApiException) {
return#Function Observable.error(t)
}
var genericResponse: GenericResponse<*>? = null
return#Function Observable.error(ApiException(t.message ?: "", genericResponse?.result ?: Result()))
})
.observeOn(mainScheduler)
.subscribeOn(ioScheduler)
}
}
}
}
And in your test:
#Before fun setup() {
RxUtils.mainScheduler = Schedulers.trampoline()
RxUtils.ioScheduler = Schedulers.trampoline()
}
#After fun teardown() {
RxUtils.mainScheduler = AndroidSchedulers.mainThread()
RxUtils.ioScheduler = Schedulers.io()
}
EDIT in response to updated post with more information on test
First of all, you should post WAY MORE CODE. It's frustrating having to pull it out of you by dribs and drabs. Anyway. You have the following:
#Mock
private UserService userService;
That creates a mock UserService, sure, but it doesn't stub anything. When you call userService.anyFunctionAtAll(), it will return null by default. There's your NPE. You have to stub it. For example:
Mockito.when(userService.anyFunctionAtAll()).thenReturn(somePredeterminedValue)
Please refer to the Mockito website for more information.