### Question:
RxSpring4Util { public static <T, R extends Iterable<T>> Function<Observable<T>, DeferredResult<R>> observableToDeferredResult( Function<? super List<T>, R> collector) { return observableToDeferredResult(collector, new DeferredResult<>()); } private  RxSpring4Util(); static Function<Single<T>, DeferredResult<T>> singleToDeferredResult(); static Function<Single<T>, DeferredResult<T>> singleToDeferredResult(
      Duration timeout); static Function<Maybe<T>, DeferredResult<T>> maybeToDeferredResult(); static Function<Maybe<T>, DeferredResult<T>> maybeToDeferredResult(Duration timeout); static Function<Observable<T>, DeferredResult<R>> observableToDeferredResult(
          Function<? super List<T>, R> collector); static Function<Observable<T>, DeferredResult<R>> observableToDeferredResult(
          Function<? super List<T>, R> collector, Duration timeout); static Function<Publisher<T>, DeferredResult<R>> publisherToDeferredResult(
          Function<? super List<T>, R> collector); static Function<Publisher<T>, DeferredResult<R>> publisherToDeferredResult(
          Function<? super List<T>, R> collector, Duration timeout); static Function<Completable, DeferredResult<Void>> completableToDeferredResult(); static Function<Completable, DeferredResult<Void>> completableToDeferredResult(
      Duration timeout); static Function<Observable<?>, SseEmitter> observableToSse(); static Function<Observable<?>, SseEmitter> observableToSse(@Nullable MediaType mediaType); static Function<Observable<?>, SseEmitter> observableToSse(
      @Nullable MediaType mediaType, Duration timeout); static Function<Publisher<?>, SseEmitter> publisherToSse(); static Function<Publisher<? extends T>, SseEmitter> publisherToSse(
      Duration heartbeat, LongFunction<T> heartbeatMapping); static Function<Publisher<? extends T>, SseEmitter> publisherToSse(
      @Nullable MediaType mediaType, Duration heartbeat, LongFunction<T> heartbeatMapping); static Function<Publisher<?>, SseEmitter> publisherToSse(@Nullable MediaType mediaType); static Function<Publisher<?>, SseEmitter> publisherToSse(Duration timeout); static Function<Publisher<?>, SseEmitter> publisherToSse(
      @Nullable MediaType mediaType, Duration timeout); static final Duration NO_TIMEOUT; }### Answer:
@Test void testObservableToDeferredResult() throws Exception { verifyAsyncGetRequest("/observableToDeferredResult?value=foo", OK, "[\"foo\"]"); verifyAsyncGetRequest( "/observableToDeferredResult?value=bar&repeat=2", OK, "[\"bar\",\"bar\"]"); verifyAsyncGetRequest("/observableToDeferredResult?value=baz&repeat=0", OK, "[]"); verifyAsyncGetRequest("/observableToDeferredResult?value=error", BAD_REQUEST, ""); }