@Test
public void testFunc0() {

    Func0<Integer> func = new Func0<Integer>() {
        @Override
        public Integer call() {
            return 0;
        }
    };
    Async.toAsync(func, Schedulers.immediate())
            .call()
            .subscribe(new TestObserver<Object>(observer));
    verify(observer, never()).onError(any(Throwable.class));
    verify(observer, times(1)).onNext(0);
    verify(observer, times(1)).onCompleted();
}