1 files changed, 41 insertions, 0 deletions
diff --git a/third_party/rust/futures/tests/future_join_all.rs b/third_party/rust/futures/tests/future_join_all.rs
new file mode 100644
index 0000000000..44486e1ca3
--- /dev/null
+++ b/third_party/rust/futures/tests/future_join_all.rs
@@ -0,0 +1,41 @@
+use futures::executor::block_on;
+use futures::future::{join_all, ready, Future, JoinAll};
+use futures::pin_mut;
+use std::fmt::Debug;
+
+#[track_caller]
+fn assert_done<T>(actual_fut: impl Future<Output = T>, expected: T)
+where
+    T: PartialEq + Debug,
+{
+    pin_mut!(actual_fut);
+    let output = block_on(actual_fut);
+    assert_eq!(output, expected);
+}
+
+#[test]
+fn collect_collects() {
+    assert_done(join_all(vec![ready(1), ready(2)]), vec![1, 2]);
+    assert_done(join_all(vec![ready(1)]), vec![1]);
+    // REVIEW: should this be implemented?
+    // assert_done(join_all(Vec::<i32>::new()), vec![]);
+
+    // TODO: needs more tests
+}
+
+#[test]
+fn join_all_iter_lifetime() {
+    // In futures-rs version 0.1, this function would fail to typecheck due to an overly
+    // conservative type parameterization of `JoinAll`.
+    fn sizes(bufs: Vec<&[u8]>) -> impl Future<Output = Vec<usize>> {
+        let iter = bufs.into_iter().map(|b| ready::<usize>(b.len()));
+        join_all(iter)
+    }
+
+    assert_done(sizes(vec![&[1, 2, 3], &[], &[0]]), vec![3_usize, 0, 1]);
+}
+
+#[test]
+fn join_all_from_iter() {
+    assert_done(vec![ready(1), ready(2)].into_iter().collect::<JoinAll<_>>(), vec![1, 2])
+}