Add tests for deadlock

bb8/tests/test.rs

@@ -317,6 +317,55 @@ async fn test_get_timeout() {
     ready(r).await.unwrap();
 }
 
+#[tokio::test]
+async fn test_lots_of_waiters() {
+    let pool = Pool::builder()
+        .max_size(3)
+        .connection_timeout(Duration::from_millis(5_000))
+        .build(OkManager::<FakeConnection>::new())
+        .await
+        .unwrap();
+
+    let mut waiters: Vec<oneshot::Receiver<()>> = Vec::new();
+
+    for _ in 0..25000 {
+        let pool = pool.clone();
+        let (tx, rx) = oneshot::channel();
+        waiters.push(rx);
+        tokio::spawn(async move {
+            let _conn = pool.get().await.unwrap();
+            tx.send(()).unwrap();
+        });
+    }
+
+    let results = futures_util::future::join_all(&mut waiters).await;
+
+    for result in results {
+        assert!(result.is_ok());
+    }
+}
+
+#[tokio::test]
+async fn test_timeout_caller() {
+    let pool = Pool::builder()
+        .max_size(1)
+        .connection_timeout(Duration::from_millis(5_000))
+        .build(OkManager::<FakeConnection>::new())
+        .await
+        .unwrap();
+
+    let one = pool.get().await;
+    assert!(one.is_ok());
+
+    let res = tokio::time::timeout(Duration::from_millis(100), pool.get()).await;
+    assert!(res.is_err());
+
+    drop(one);
+
+    let two = pool.get().await;
+    assert!(two.is_ok());
+}
+
 #[tokio::test]
 async fn test_now_invalid() {
     static INVALID: AtomicBool = AtomicBool::new(false);