1 files changed, 58 insertions, 0 deletions
diff --git a/third_party/rust/futures/tests/stream_peekable.rs b/third_party/rust/futures/tests/stream_peekable.rs
new file mode 100644
index 0000000000..153fcc25b4
--- /dev/null
+++ b/third_party/rust/futures/tests/stream_peekable.rs
@@ -0,0 +1,58 @@
+use futures::executor::block_on;
+use futures::pin_mut;
+use futures::stream::{self, Peekable, StreamExt};
+
+#[test]
+fn peekable() {
+    block_on(async {
+        let peekable: Peekable<_> = stream::iter(vec![1u8, 2, 3]).peekable();
+        pin_mut!(peekable);
+        assert_eq!(peekable.as_mut().peek().await, Some(&1u8));
+        assert_eq!(peekable.collect::<Vec<u8>>().await, vec![1, 2, 3]);
+
+        let s = stream::once(async { 1 }).peekable();
+        pin_mut!(s);
+        assert_eq!(s.as_mut().peek().await, Some(&1u8));
+        assert_eq!(s.collect::<Vec<u8>>().await, vec![1]);
+    });
+}
+
+#[test]
+fn peekable_mut() {
+    block_on(async {
+        let s = stream::iter(vec![1u8, 2, 3]).peekable();
+        pin_mut!(s);
+        if let Some(p) = s.as_mut().peek_mut().await {
+            if *p == 1 {
+                *p = 5;
+            }
+        }
+        assert_eq!(s.collect::<Vec<_>>().await, vec![5, 2, 3]);
+    });
+}
+
+#[test]
+fn peekable_next_if_eq() {
+    block_on(async {
+        // first, try on references
+        let s = stream::iter(vec!["Heart", "of", "Gold"]).peekable();
+        pin_mut!(s);
+        // try before `peek()`
+        assert_eq!(s.as_mut().next_if_eq(&"trillian").await, None);
+        assert_eq!(s.as_mut().next_if_eq(&"Heart").await, Some("Heart"));
+        // try after peek()
+        assert_eq!(s.as_mut().peek().await, Some(&"of"));
+        assert_eq!(s.as_mut().next_if_eq(&"of").await, Some("of"));
+        assert_eq!(s.as_mut().next_if_eq(&"zaphod").await, None);
+        // make sure `next()` still behaves
+        assert_eq!(s.next().await, Some("Gold"));
+
+        // make sure comparison works for owned values
+        let s = stream::iter(vec![String::from("Ludicrous"), "speed".into()]).peekable();
+        pin_mut!(s);
+        // make sure basic functionality works
+        assert_eq!(s.as_mut().next_if_eq("Ludicrous").await, Some("Ludicrous".into()));
+        assert_eq!(s.as_mut().next_if_eq("speed").await, Some("speed".into()));
+        assert_eq!(s.as_mut().next_if_eq("").await, None);
+    });
+}