add another test

test/dune

@@ -11,6 +11,7 @@
   t_resource
   t_unfair
   t_ws_deque
+  t_ws_wait
   t_bounded_queue)
  (libraries
   moonpool

test/t_ws_wait.ml

@@ -0,0 +1,21 @@
+open! Moonpool
+
+let ( let@ ) = ( @@ )
+
+let () =
+  let sum = Atomic.make 0 in
+  let n = 300_000 in
+
+  (let@ pool = Ws_pool.with_ ~num_threads:30 () in
+   for _i = 1 to n do
+     Runner.run_async pool (fun () ->
+         Thread.yield ();
+         ignore (Atomic.fetch_and_add sum 20 : int))
+   done;
+   Runner.shutdown pool);
+
+  (* make sure that shutdown didn't terminate before
+     all tasks were run *)
+  let sum = Atomic.get sum in
+  assert (sum = 20 * n);
+  ()