1 files changed, 60 insertions, 0 deletions
diff --git a/library/std/src/sync/reentrant_lock/tests.rs b/library/std/src/sync/reentrant_lock/tests.rs
new file mode 100644
index 00000000000..d4c1d440c61
--- /dev/null
+++ b/library/std/src/sync/reentrant_lock/tests.rs
@@ -0,0 +1,60 @@
+use super::{ReentrantLock, ReentrantLockGuard};
+use crate::cell::RefCell;
+use crate::sync::Arc;
+use crate::thread;
+
+#[test]
+fn smoke() {
+    let l = ReentrantLock::new(());
+    {
+        let a = l.lock();
+        {
+            let b = l.lock();
+            {
+                let c = l.lock();
+                assert_eq!(*c, ());
+            }
+            assert_eq!(*b, ());
+        }
+        assert_eq!(*a, ());
+    }
+}
+
+#[test]
+fn is_mutex() {
+    let l = Arc::new(ReentrantLock::new(RefCell::new(0)));
+    let l2 = l.clone();
+    let lock = l.lock();
+    let child = thread::spawn(move || {
+        let lock = l2.lock();
+        assert_eq!(*lock.borrow(), 4950);
+    });
+    for i in 0..100 {
+        let lock = l.lock();
+        *lock.borrow_mut() += i;
+    }
+    drop(lock);
+    child.join().unwrap();
+}
+
+#[test]
+fn trylock_works() {
+    let l = Arc::new(ReentrantLock::new(()));
+    let l2 = l.clone();
+    let _lock = l.try_lock();
+    let _lock2 = l.try_lock();
+    thread::spawn(move || {
+        let lock = l2.try_lock();
+        assert!(lock.is_none());
+    })
+    .join()
+    .unwrap();
+    let _lock3 = l.try_lock();
+}
+
+pub struct Answer<'a>(pub ReentrantLockGuard<'a, RefCell<u32>>);
+impl Drop for Answer<'_> {
+    fn drop(&mut self) {
+        *self.0.borrow_mut() = 42;
+    }
+}