@@ -51,3 +51,46 @@ pub fn is_managed(pid: i32) -> bool {
         .lock()
         .is_ok_and(|children| children.contains(&pid))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{is_managed, register, unregister};
+    use nix::sys::wait::{Id, WaitPidFlag, WaitStatus, waitid, waitpid};
+    use nix::unistd::Pid;
+    use std::process::Command;
+
+    #[test]
+    fn fast_child_remains_waitable_after_orphan_reap_attempt() {
+        let mut child = Command::new("sh")
+            .args(["-c", "exit 11"])
+            .spawn()
+            .expect("spawn fast child");
+        let child_pid = child.id();
+        let pid = Pid::from_raw(i32::try_from(child_pid).unwrap());
+
+        // Observe the completed child without consuming its status, exactly
+        // as the orphan reaper does before its managed-PID check.
+        loop {
+            match waitid(
+                Id::Pid(pid),
+                WaitPidFlag::WEXITED | WaitPidFlag::WNOHANG | WaitPidFlag::WNOWAIT,
+            ) {
+                Ok(WaitStatus::StillAlive) => std::thread::yield_now(),
+                Ok(_) => break,
+                Err(error) => panic!("observe fast child: {error}"),
+            }
+        }
+
+        if !is_managed(pid.as_raw()) {
+            waitpid(pid, Some(WaitPidFlag::WNOHANG)).expect("orphan reaper consumes child");
+        }
+        register(child_pid);
+
+        let wait = child.wait();
+        unregister(child_pid);
+        assert!(
+            wait.is_ok(),
+            "the explicit child waiter must retain the exit status"
+        );
+    }
+}