third_party/rust_crates/vendor/futures-preview/tests/futures_ordered.rs

use futures::channel::oneshot;
use futures::executor::{block_on, block_on_stream};
use futures::future::{self, join, FutureExt};
use futures::stream::{StreamExt, FuturesOrdered};
use futures_test::task::noop_context;

#[test]
fn works_1() {
    let (a_tx, a_rx) = oneshot::channel::<i32>();
    let (b_tx, b_rx) = oneshot::channel::<i32>();
    let (c_tx, c_rx) = oneshot::channel::<i32>();

    let mut stream = vec![a_rx, b_rx, c_rx].into_iter().collect::<FuturesOrdered<_>>();

    b_tx.send(99).unwrap();
    assert!(stream.poll_next_unpin(&mut noop_context()).is_pending());

    a_tx.send(33).unwrap();
    c_tx.send(33).unwrap();

    let mut iter = block_on_stream(stream);
    assert_eq!(Some(Ok(33)), iter.next());
    assert_eq!(Some(Ok(99)), iter.next());
    assert_eq!(Some(Ok(33)), iter.next());
    assert_eq!(None, iter.next());
}

#[test]
fn works_2() {
    let (a_tx, a_rx) = oneshot::channel::<i32>();
    let (b_tx, b_rx) = oneshot::channel::<i32>();
    let (c_tx, c_rx) = oneshot::channel::<i32>();

    let mut stream = vec![
        a_rx.boxed(),
        join(b_rx, c_rx).map(|(a, b)| Ok(a? + b?)).boxed(),
    ].into_iter().collect::<FuturesOrdered<_>>();

    let mut cx = noop_context();
    a_tx.send(33).unwrap();
    b_tx.send(33).unwrap();
    assert!(stream.poll_next_unpin(&mut cx).is_ready());
    assert!(stream.poll_next_unpin(&mut cx).is_pending());
    c_tx.send(33).unwrap();
    assert!(stream.poll_next_unpin(&mut cx).is_ready());
}

#[test]
fn from_iterator() {
    let stream = vec![
        future::ready::<i32>(1),
        future::ready::<i32>(2),
        future::ready::<i32>(3)
    ].into_iter().collect::<FuturesOrdered<_>>();
    assert_eq!(stream.len(), 3);
    assert_eq!(block_on(stream.collect::<Vec<_>>()), vec![1,2,3]);
}

/* ToDo: This requires FutureExt::select to be implemented
#[test]
fn queue_never_unblocked() {
    let (_a_tx, a_rx) = oneshot::channel::<Box<Any+Send>>();
    let (b_tx, b_rx) = oneshot::channel::<Box<Any+Send>>();
    let (c_tx, c_rx) = oneshot::channel::<Box<Any+Send>>();

    let mut stream = vec![
        Box::new(a_rx) as Box<Future<Item = _, Error = _>>,
        Box::new(b_rx.select(c_rx).then(|res| Ok(Box::new(res) as Box<Any+Send>))) as _,
    ].into_iter().collect::<FuturesOrdered<_>>();

    with_no_spawn_context(|cx| {
        for _ in 0..10 {
            assert!(stream.poll_next(cx).unwrap().is_pending());
        }

        b_tx.send(Box::new(())).unwrap();
        assert!(stream.poll_next(cx).unwrap().is_pending());
        c_tx.send(Box::new(())).unwrap();
        assert!(stream.poll_next(cx).unwrap().is_pending());
        assert!(stream.poll_next(cx).unwrap().is_pending());
    })
}*/