Unit test verify method was called inside RxJava's doOnSuccess operator - unit-testing

Question

I have the following code I'm trying to unit test :
if (networkUtils.isOnline()) {
return remoteDataSource.postComment(postId, commentText)
.doOnSuccess(postCommentResponse ->
localDataSource.postComment(postId, commentText))
.subscribeOn(schedulerProvider.io())
.observeOn(schedulerProvider.mainThread());
} else {
return Single.error(new IOException());
}
And this is how I'm trying to test it :
#Test
public void postComment_whenIsOnline_shouldCallLocalToPostComment() throws Exception {
// Given
when(networkUtils.isOnline())
.thenReturn(true);
String postId = "100";
String comment = "comment";
Response<PostCommentResponse> response = postCommentResponse();
when(remoteDataSource.postComment(anyString(), anyString()))
.thenReturn(Single.just(response));
// When
repository.postComment(postId, comment);
// Then
verify(localDataSource).postComment(postId, comment);
}
where I fake Response from Retrofit like :
private Response<PostCommentResponse> postCommentResponse() {
PostCommentResponse response = new PostCommentResponse();
response.setError("0");
response.setComment(postCommentResponseNestedItem);
return Response.success(response);
}
but it results to : Actually, there were zero interactions with this mock.
Any ideas ?
EDIT :
#RunWith(MockitoJUnitRunner.class)
public class CommentsRepositoryTest {
#Mock
private CommentsLocalDataSource localDataSource;
#Mock
private CommentsRemoteDataSource remoteDataSource;
#Mock
private NetworkUtils networkUtils;
#Mock
private PostCommentResponseNestedItem postCommentResponseNestedItem;
private CommentsRepository repository;
#Before
public void setUp() throws Exception {
MockitoAnnotations.initMocks(this);
BaseSchedulerProvider schedulerProvider = new ImmediateSchedulerProvider();
repository = new CommentsRepository(localDataSource, remoteDataSource, networkUtils, schedulerProvider);
}
// tests
}

Answer 1

When you want to test an Observable you have to subscribe to it so it will start emitting items.
As soon as I used :
TestObserver<Response<PostCommentResponse>> testObserver = new TestObserver<>();
and subscribed to :
repository.postComment(postId, comment)
.subscribe(testObserver);
the test worked as expected.