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use tokio::stream::{self, Stream, StreamExt};
use tokio::sync::mpsc;
use tokio_test::{assert_pending, assert_ready, task};
#[tokio::test]
async fn basic_usage() {
let one = stream::iter(vec![1, 2, 3]);
let two = stream::iter(vec![4, 5, 6]);
let mut stream = one.chain(two);
assert_eq!(stream.size_hint(), (6, Some(6)));
assert_eq!(stream.next().await, Some(1));
assert_eq!(stream.size_hint(), (5, Some(5)));
assert_eq!(stream.next().await, Some(2));
assert_eq!(stream.size_hint(), (4, Some(4)));
assert_eq!(stream.next().await, Some(3));
assert_eq!(stream.size_hint(), (3, Some(3)));
assert_eq!(stream.next().await, Some(4));
assert_eq!(stream.size_hint(), (2, Some(2)));
assert_eq!(stream.next().await, Some(5));
assert_eq!(stream.size_hint(), (1, Some(1)));
assert_eq!(stream.next().await, Some(6));
assert_eq!(stream.size_hint(), (0, Some(0)));
assert_eq!(stream.next().await, None);
assert_eq!(stream.size_hint(), (0, Some(0)));
assert_eq!(stream.next().await, None);
}
#[tokio::test]
async fn pending_first() {
let (tx1, rx1) = mpsc::unbounded_channel();
let (tx2, rx2) = mpsc::unbounded_channel();
let mut stream = task::spawn(rx1.chain(rx2));
assert_eq!(stream.size_hint(), (0, None));
assert_pending!(stream.poll_next());
tx2.send(2).unwrap();
assert!(!stream.is_woken());
assert_pending!(stream.poll_next());
tx1.send(1).unwrap();
assert!(stream.is_woken());
assert_eq!(Some(1), assert_ready!(stream.poll_next()));
assert_pending!(stream.poll_next());
drop(tx1);
assert_eq!(stream.size_hint(), (0, None));
assert!(stream.is_woken());
assert_eq!(Some(2), assert_ready!(stream.poll_next()));
assert_eq!(stream.size_hint(), (0, None));
drop(tx2);
assert_eq!(stream.size_hint(), (0, None));
assert_eq!(None, assert_ready!(stream.poll_next()));
}
#[test]
fn size_overflow() {
struct Monster;
impl tokio::stream::Stream for Monster {
type Item = ();
fn poll_next(
self: std::pin::Pin<&mut Self>,
_cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Option<()>> {
panic!()
}
fn size_hint(&self) -> (usize, Option<usize>) {
(usize::max_value(), Some(usize::max_value()))
}
}
let m1 = Monster;
let m2 = Monster;
let m = m1.chain(m2);
assert_eq!(m.size_hint(), (usize::max_value(), None));
}
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