let%expect_test _ =
  let print_list print_ele xs =
    let rec iter pre post = function
      | [] -> print_string post
      | x :: xs ->
        print_string pre;
        print_ele x;
        iter ";" "]" xs
    in
    iter "[" "[]" xs
  in

  let print_history_nl ch k =
    print_list print_int (Cache.find_all ch k);
    print_newline ()
  in

  let ch = Cache.make 4 in
  Cache.add ch "x" 1;
  Cache.add ch "y" 2;
  Cache.add ch "y" 3;
  Cache.add ch "z" 4;

  print_history_nl ch "x"; [%expect {| [1] |}];
  print_history_nl ch "y"; [%expect {| [3;2] |}];
  print_history_nl ch "z"; [%expect {| [4] |}];
  print_history_nl ch "w"; [%expect {| [] |}];

  Cache.add ch "w" 5; (* evict "x:=1" *)

  print_history_nl ch "x"; [%expect {| [] |}];
  print_history_nl ch "y"; [%expect {| [3;2] |}];
  print_history_nl ch "z"; [%expect {| [4] |}];
  print_history_nl ch "w"; [%expect {| [5] |}];

  Cache.add ch "w" 6; (* evict "y:=2" *)

  print_history_nl ch "x"; [%expect {| [] |}];
  print_history_nl ch "y"; [%expect {| [3] |}];
  print_history_nl ch "z"; [%expect {| [4] |}];
  print_history_nl ch "w"; [%expect {| [6;5] |}];

  Cache.add ch "x" 7; (* evict "y:=3" *)
  Cache.add ch "w" 8; (* evict "z:=4" *)

  print_history_nl ch "x"; [%expect {| [7] |}];
  print_history_nl ch "y"; [%expect {| [] |}];
  print_history_nl ch "z"; [%expect {| [] |}];
  print_history_nl ch "w"; [%expect {| [8;6;5] |}];