test: add more fork-join tests

test/effect-based/dune

@@ -1,7 +1,7 @@
 
 (tests
   (names t_fib1 t_futs1 t_many t_fib_fork_join
-         t_fib_fork_join_all t_sort)
+         t_fib_fork_join_all t_sort t_fork_join)
   (enabled_if (>= %{ocaml_version} 5.0))
   (libraries moonpool trace ;tracy-client.trace
              ))

test/effect-based/t_fork_join.ml

@@ -0,0 +1,38 @@
+open Moonpool
+
+let pool = Pool.create ~min:4 ()
+
+let () =
+  let x =
+    Pool.run_wait_block pool (fun () ->
+        let x, y =
+          Fork_join.both
+            (fun () ->
+              Thread.delay 0.005;
+              1)
+            (fun () ->
+              Thread.delay 0.005;
+              2)
+        in
+        x + y)
+  in
+  assert (x = 3)
+
+let () =
+  try
+    Pool.run_wait_block pool (fun () ->
+        Fork_join.both_ignore
+          (fun () -> Thread.delay 0.005)
+          (fun () ->
+            Thread.delay 0.02;
+            raise Exit));
+    failwith "should fail"
+  with Exit -> ()
+
+let () =
+  let par_sum =
+    Pool.run_wait_block pool (fun () ->
+        Fork_join.all_init 42 (fun i -> i * i) |> List.fold_left ( + ) 0)
+  in
+  let exp_sum = List.init 42 (fun x -> x * x) |> List.fold_left ( + ) 0 in
+  assert (par_sum = exp_sum)