OperationDefer { public static <T> OnSubscribeFunc<T> defer(final Func0<? extends Observable<? extends T>> observableFactory) { return new OnSubscribeFunc<T>() { @Override public Subscription onSubscribe(Observer<? super T> observer) { Observable<? extends T> obs = observableFactory.call(); return obs.subscribe(observer); } }; }  static OnSubscribeFunc<T> defer(final Func0<? extends Observable<? extends T>> observableFactory);  }
@Test @SuppressWarnings("unchecked") public void testDefer() throws Throwable { Func0<Observable<String>> factory = mock(Func0.class); Observable<String> firstObservable = Observable.from("one", "two"); Observable<String> secondObservable = Observable.from("three", "four"); when(factory.call()).thenReturn(firstObservable, secondObservable); Observable<String> deferred = Observable.defer(factory); verifyZeroInteractions(factory); Observer<String> firstObserver = mock(Observer.class); deferred.subscribe(firstObserver); verify(factory, times(1)).call(); verify(firstObserver, times(1)).onNext("one"); verify(firstObserver, times(1)).onNext("two"); verify(firstObserver, times(0)).onNext("three"); verify(firstObserver, times(0)).onNext("four"); verify(firstObserver, times(1)).onCompleted(); Observer<String> secondObserver = mock(Observer.class); deferred.subscribe(secondObserver); verify(factory, times(2)).call(); verify(secondObserver, times(0)).onNext("one"); verify(secondObserver, times(0)).onNext("two"); verify(secondObserver, times(1)).onNext("three"); verify(secondObserver, times(1)).onNext("four"); verify(secondObserver, times(1)).onCompleted(); }