Mockito thenAnswer doesn't seem to work as expected

Question

I am writing unit test for the following code which uses AsyncHttpClient. The use of CountDownLatch and decrementing of the CountDownLatch within the implementation of FutureCallback is causing my JUnit testcase to hang waiting for countdown latch to be decremented. Within the JUnit test I am capturing the FutureCallback using ArgumentCaptor and then using thenAnswer I am calling the completed method to decrement the count down latch. But it doesn't seems to work, any ideas will be helpful.

public List<QueryResponse> execute(Query query) {
    List<QueryResponse> res = new ArrayList<QueryResponse>();

    try {
        List<HttpRequestBase> requests = query.generateHttpRequests();
        List<Future<HttpResponse>> futures = new ArrayList<Future<HttpResponse>>();

        final CountDownLatch requestCompletionCDLatch = new CountDownLatch(requests.size());
        for (HttpRequestBase request : requests) {
            futures.add(httpClient.execute(request, new FutureCallback<HttpResponse>() {

                @Override
                public void failed(Exception e) {
                    logger.error("Error while executing: " + request.toString(), e);
                    requestCompletionCDLatch.countDown();
                }

                @Override
                public void completed(HttpResponse result) {
                    requestCompletionCDLatch.countDown();
                }

                @Override
                public void cancelled() {
                    logger.info("Request cancelled while executing: " + request.toString());
                    requestCompletionCDLatch.countDown();
                }
            }));
        }

        requestCompletionCDLatch.await();
        for (Future<HttpResponse> future : futures) {
            HttpResponse response = future.get(rcaRequestTimeout, TimeUnit.SECONDS);
            int status = response.getStatusLine().getStatusCode();
            if (status != HttpStatus.SC_OK) {
                logger.warn("Query with non-success status " + status);
            } else {
                res.add(query.parseResponse(response.getEntity().getContent()));
            }
        }
    } catch (IOException | InterruptedException | ExecutionException | TimeoutException e) {
        logger.error("Error while querying", e);
    } catch (URISyntaxException e) {
        logger.error("Error while generating the query", e);
    }
    return res;
}

My unit test is as follows:

@Test
public void testHttpError() throws InterruptedException, ExecutionException, TimeoutException {
    StatusLine status = Mockito.mock(StatusLine.class);
    when(status.getStatusCode()).thenReturn(400);

    HttpResponse response = Mockito.mock(HttpResponse.class);
    when(response.getStatusLine()).thenReturn(status);

    Future<HttpResponse> future = Mockito.mock(Future.class);
    when(future.get(anyLong(), any())).thenReturn(response);

    CloseableHttpAsyncClient httpClient = Mockito.mock(CloseableHttpAsyncClient.class);
    ArgumentCaptor<HttpUriRequest> requestCaptor = ArgumentCaptor.forClass(HttpUriRequest.class);
    ArgumentCaptor<FutureCallback<HttpResponse>> futureCallbackCaptor = ArgumentCaptor.forClass((Class)FutureCallback.class);
    when(httpClient.execute(any(), any())).thenReturn(future).thenAnswer(new Answer() {

        @Override
        public Object answer(InvocationOnMock invocation) throws Throwable {
            verify(httpClient).execute(requestCaptor.capture(), futureCallbackCaptor.capture());
            futureCallbackCaptor.getValue().completed(response);
            return null;
        }
    });

    StubbedRcaClient rcaClient = new StubbedRcaClient(httpClient);
    Query query = new Query("abc", "xyz", RcaHttpRequestType.GET, 1000);
    List<QueryResponse> res = rcaClient.execute(query);
    assertEquals(0, res.size());
    IOUtils.closeQuietly(rcaClient);
}

This test is extremely complex, including the logic for verifying in the answer. Maybe you can refactor it to make it easier for the community and maintenance programmer to understand? Look at some of the examples of good unit tests somewhere like https://dzone.com/refcardz/mockito for example. There is a clear structure given/when/then. In terms of making the unit test work as expected, what is `StubbedRcaClient` and is it correctly delegating to `httpClient`? Also, don't mock `Future` - you don't know if the callback is using `get(long, TimeUnit)` or another method inside `Future` — David Rawson, Nov 09 '16 at 07:35
I am trying to mock the responses from HttpAsyncClient, if I don't mock Future what do you suggest? — KunalC, Nov 09 '16 at 19:11
https://stackoverflow.com/questions/13866533/how-to-create-a-completed-future-in-java — David Rawson, Nov 09 '16 at 19:15

score 0 · Accepted Answer · answered Nov 09 '16 at 21:06

I made this work by updating my JUnit as follows:

when(httpClient.execute(any(), any())).thenAnswer(new Answer<Future<HttpResponse>>() {

    @Override
    public Future<HttpResponse> answer(InvocationOnMock invocation) throws Throwable {
        verify(httpClient).execute(requestCaptor.capture(), futureCallbackCaptor.capture());
        futureCallbackCaptor.getValue().completed(response);
        return future;
    }
});

Mockito thenAnswer doesn't seem to work as expected

1 Answers1