let () =
  let test_sources = [
    "(define foo 42)";
    ";; comment\n(define bar 1)\n\n;; another\n(define baz 2)\n";
    "(define my-fn\n  (fn (x)\n    ;; check nil\n    (if (nil? x) 0 x)))";
    "(list 1 2 3)";
    "{:key \"value\" :num 42}";
    "'(a b c)";
    "`(a ,b ,@c)";
    "(define x \"hello\\nworld\")";
    ";; top\n;; multi-line\n(define a 1)\n";
    "";
    "  \n  ";
    "(a)\n(b)\n(c)";
    "(a ;; inline\n  b)";
  ] in
  let pass = ref 0 in
  let fail = ref 0 in
  List.iter (fun src ->
    let cst = Sx_parser.parse_all_cst src in
    let roundtrip = Sx_cst.cst_file_to_source cst.nodes cst.trailing_trivia in
    if roundtrip = src then begin
      incr pass;
      Printf.printf "PASS: %S\n" (if String.length src > 40 then String.sub src 0 40 ^ "..." else src)
    end else begin
      incr fail;
      Printf.printf "FAIL: %S\n  expected: %S\n  got:      %S\n"
        (if String.length src > 40 then String.sub src 0 40 ^ "..." else src)
        src roundtrip
    end
  ) test_sources;
  (* Also test CST→AST matches AST parser *)
  let ast_tests = [
    "(define foo 42)";
    "(list 1 2 3)";
    "{:key \"value\"}";
    ";; comment\n(define bar 1)";
  ] in
  Printf.printf "\nCST→AST equivalence:\n";
  List.iter (fun src ->
    let ast_direct = Sx_parser.parse_all src in
    let cst = Sx_parser.parse_all_cst src in
    let ast_via_cst = List.map Sx_cst.cst_to_ast cst.nodes in
    let s1 = String.concat " " (List.map Sx_types.inspect ast_direct) in
    let s2 = String.concat " " (List.map Sx_types.inspect ast_via_cst) in
    if s1 = s2 then begin
      incr pass;
      Printf.printf "PASS: %S\n" src
    end else begin
      incr fail;
      Printf.printf "FAIL: %S\n  AST:     %s\n  CST→AST: %s\n" src s1 s2
    end
  ) ast_tests;
  (* Test real .sx files from the codebase *)
  Printf.printf "\nReal file round-trips:\n";
  let test_file path =
    try
      let src = In_channel.with_open_text path In_channel.input_all in
      let cst = Sx_parser.parse_all_cst src in
      let roundtrip = Sx_cst.cst_file_to_source cst.nodes cst.trailing_trivia in
      if roundtrip = src then begin
        incr pass;
        Printf.printf "PASS: %s (%d bytes)\n" path (String.length src)
      end else begin
        incr fail;
        (* Find first difference *)
        let len = min (String.length src) (String.length roundtrip) in
        let diff_pos = ref len in
        for i = 0 to len - 1 do
          if src.[i] <> roundtrip.[i] && !diff_pos = len then diff_pos := i
        done;
        Printf.printf "FAIL: %s (diff at byte %d, src=%d rt=%d)\n" path !diff_pos (String.length src) (String.length roundtrip)
      end
    with e ->
      incr fail;
      Printf.printf "ERROR: %s — %s\n" path (Printexc.to_string e)
  in
  let spec_dir = try Sys.getenv "SX_SPEC_DIR" with Not_found -> "spec" in
  let project_dir = try Sys.getenv "SX_PROJECT_DIR" with Not_found -> "." in
  List.iter test_file [
    spec_dir ^ "/evaluator.sx";
    spec_dir ^ "/parser.sx";
    spec_dir ^ "/primitives.sx";
    spec_dir ^ "/render.sx";
    project_dir ^ "/lib/tree-tools.sx";
    project_dir ^ "/web/engine.sx";
    project_dir ^ "/web/io.sx";
  ];

  Printf.printf "\n%d/%d passed\n" !pass (!pass + !fail);
  if !fail > 0 then exit 1