1 files changed, 67 insertions, 0 deletions
diff --git a/tests/lock_mutex.rs b/tests/lock_mutex.rs
new file mode 100644
index 0000000..c92ef50
--- /dev/null
+++ b/tests/lock_mutex.rs
@@ -0,0 +1,67 @@
+use futures::channel::mpsc;
+use futures::executor::{block_on, ThreadPool};
+use futures::future::{ready, FutureExt};
+use futures::lock::Mutex;
+use futures::stream::StreamExt;
+use futures::task::{Context, SpawnExt};
+use futures_test::future::FutureTestExt;
+use futures_test::task::{new_count_waker, panic_context};
+use std::sync::Arc;
+
+#[test]
+fn mutex_acquire_uncontested() {
+    let mutex = Mutex::new(());
+    for _ in 0..10 {
+        assert!(mutex.lock().poll_unpin(&mut panic_context()).is_ready());
+    }
+}
+
+#[test]
+fn mutex_wakes_waiters() {
+    let mutex = Mutex::new(());
+    let (waker, counter) = new_count_waker();
+    let lock = mutex.lock().poll_unpin(&mut panic_context());
+    assert!(lock.is_ready());
+
+    let mut cx = Context::from_waker(&waker);
+    let mut waiter = mutex.lock();
+    assert!(waiter.poll_unpin(&mut cx).is_pending());
+    assert_eq!(counter, 0);
+
+    drop(lock);
+
+    assert_eq!(counter, 1);
+    assert!(waiter.poll_unpin(&mut panic_context()).is_ready());
+}
+
+#[cfg_attr(miri, ignore)] // https://github.com/rust-lang/miri/issues/1038
+#[test]
+fn mutex_contested() {
+    let (tx, mut rx) = mpsc::unbounded();
+    let pool = ThreadPool::builder().pool_size(16).create().unwrap();
+
+    let tx = Arc::new(tx);
+    let mutex = Arc::new(Mutex::new(0));
+
+    let num_tasks = 1000;
+    for _ in 0..num_tasks {
+        let tx = tx.clone();
+        let mutex = mutex.clone();
+        pool.spawn(async move {
+            let mut lock = mutex.lock().await;
+            ready(()).pending_once().await;
+            *lock += 1;
+            tx.unbounded_send(()).unwrap();
+            drop(lock);
+        })
+        .unwrap();
+    }
+
+    block_on(async {
+        for _ in 0..num_tasks {
+            rx.next().await.unwrap();
+        }
+        let lock = mutex.lock().await;
+        assert_eq!(num_tasks, *lock);
+    })
+}