use tokio_stream::{self as stream, Stream, StreamExt}; use tokio_test::{assert_pending, assert_ready, task}; mod support { pub(crate) mod mpsc; } use support::mpsc; #[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_stream(); let (tx2, rx2) = mpsc::unbounded_channel_stream(); 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> { panic!() } fn size_hint(&self) -> (usize, Option) { (usize::MAX, Some(usize::MAX)) } } let m1 = Monster; let m2 = Monster; let m = m1.chain(m2); assert_eq!(m.size_hint(), (usize::MAX, None)); }