1 files changed, 65 insertions, 0 deletions
diff --git a/third_party/rust/crossbeam-utils/tests/wait_group.rs b/third_party/rust/crossbeam-utils/tests/wait_group.rs
new file mode 100644
index 0000000000..0ec4a729ca
--- /dev/null
+++ b/third_party/rust/crossbeam-utils/tests/wait_group.rs
@@ -0,0 +1,65 @@
+use std::sync::mpsc;
+use std::thread;
+use std::time::Duration;
+
+use crossbeam_utils::sync::WaitGroup;
+
+const THREADS: usize = 10;
+
+#[test]
+fn wait() {
+    let wg = WaitGroup::new();
+    let (tx, rx) = mpsc::channel();
+
+    for _ in 0..THREADS {
+        let wg = wg.clone();
+        let tx = tx.clone();
+
+        thread::spawn(move || {
+            wg.wait();
+            tx.send(()).unwrap();
+        });
+    }
+
+    thread::sleep(Duration::from_millis(100));
+
+    // At this point, all spawned threads should be blocked, so we shouldn't get anything from the
+    // channel.
+    assert!(rx.try_recv().is_err());
+
+    wg.wait();
+
+    // Now, the wait group is cleared and we should receive messages.
+    for _ in 0..THREADS {
+        rx.recv().unwrap();
+    }
+}
+
+#[test]
+#[cfg_attr(miri, ignore)] // this test makes timing assumptions, but Miri is so slow it violates them
+fn wait_and_drop() {
+    let wg = WaitGroup::new();
+    let (tx, rx) = mpsc::channel();
+
+    for _ in 0..THREADS {
+        let wg = wg.clone();
+        let tx = tx.clone();
+
+        thread::spawn(move || {
+            thread::sleep(Duration::from_millis(100));
+            tx.send(()).unwrap();
+            drop(wg);
+        });
+    }
+
+    // At this point, all spawned threads should be in `thread::sleep`, so we shouldn't get anything
+    // from the channel.
+    assert!(rx.try_recv().is_err());
+
+    wg.wait();
+
+    // Now, the wait group is cleared and we should receive messages.
+    for _ in 0..THREADS {
+        rx.try_recv().unwrap();
+    }
+}