Passing the files input for tests generation in Alcotest + Dune

Learning
1

Sorry for double posting, but seems fewer people will see it on GitHub, so writing also here.
For example, if you have some binaries in the test/samples directory, and need to pass that path to the test, and having a code like

let mytest filename =
     (fun () -> Alcotest.(check string) "some" "string1" "string2")

let testset path =
     List.map ~f:(fun l ->
          l, `Slow, mytest l)
     (Sys.readdir path)

let get_tests_dir =
     let doc = "path to the tests directory" in
     Cmdliner.Arg.(required & opt (some string) None & info ["p"] ~doc ~docv:"PATH")

let () =
     Alcotest.run_with_args "my shiny tests" get_tests_dir [
        "testset1", testset;
     ]

But that wouldn’t work, because Alcotest passes the argument to each checker function separately in the test list. Is it possible to work around this somehow? So every file in the test/samples would be a separate test like “filename, `Slow, mytest filename”.
I am going to pass that path in the dune file:

(alias
 (name   runtest)
 (action (run ./tests.exe "test/samples")))

Is it possible somehow?