diff --git a/.gitignore b/.gitignore
index 7c14f3f5..76327624 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ _build
 boot.exe
 .merlin
 boot.ml
+*.corrected
diff --git a/test/expect-tests/expect_test.mll b/test/expect-tests/expect_test.mll
new file mode 100644
index 00000000..e4625dc8
--- /dev/null
+++ b/test/expect-tests/expect_test.mll
@@ -0,0 +1,128 @@
+{
+open StdLabels
+open Printf
+}
+
+rule code txt start = parse
+  | "[%%expect{|\n" {
+    let pos = start.Lexing.pos_cnum in
+    let len = Lexing.lexeme_start lexbuf - pos in
+    let s = String.sub txt ~pos ~len in
+    Lexing.new_line lexbuf;
+    (start, s) :: expectation txt lexbuf
+  }
+  | [^'\n']*'\n' {
+    Lexing.new_line lexbuf;
+    code txt start lexbuf
+  }
+  | eof {
+    let pos = start.Lexing.pos_cnum in
+    let len = String.length txt - pos in
+    if pos > 0 then begin
+      let s = String.sub txt ~pos ~len in
+      if String.trim s = "" then
+        []
+      else
+        [(start, s)]
+    end else
+      []
+  }
+
+and expectation txt = parse
+  | "|}]\n" {
+      Lexing.new_line lexbuf;
+      code txt lexbuf.lex_curr_p lexbuf
+    }
+  | [^'\n']*'\n' {
+    Lexing.new_line lexbuf;
+    expectation txt lexbuf
+  }
+
+{
+module Print_diff = struct
+  let patdiff_cmd ~use_color =
+    let args =
+      List.concat [
+        ["-keep-whitespace"];
+        ["-location-style omake"];
+        (if use_color then ["-unrefined"] else ["-ascii"]);
+      ]
+    in
+    String.concat ~sep:" " ("patdiff" :: args)
+
+  let print ?diff_command ?(use_color=false) ~file1 ~file2 () =
+    let exec cmd =
+      let cmd =
+        Printf.sprintf "%s %s %s 1>&2" cmd (Filename.quote file1) (Filename.quote file2)
+      in
+      match Sys.command cmd with
+      | 0 -> true
+      | 1 -> false
+      | n -> Printf.eprintf "%S exited with code %d\n" cmd n; exit 2
+    in
+    match diff_command with
+    | Some s -> ignore (exec s : bool)
+    | None ->
+      if exec (patdiff_cmd ~use_color) then (
+        Printf.eprintf "File \"%s\", line 1, characters 0-0:\n%!" file1;
+        ignore (exec "diff -u" : bool);
+      )
+end
+
+let main () =
+  let fn = Sys.argv.(1) in
+  let ic = open_in_bin fn in
+  let len = in_channel_length ic in
+  let txt = really_input_string ic len in
+  close_in ic;
+  let chunks =
+    let lexbuf = Lexing.from_string txt in
+    lexbuf.lex_curr_p <-
+      { pos_fname = fn
+      ; pos_cnum  = 0
+      ; pos_lnum  = 1
+      ; pos_bol   = 0
+      };
+    code txt lexbuf.lex_curr_p lexbuf
+  in
+
+  Toploop.initialize_toplevel_env ();
+  List.iter
+    [ "src"
+    ; "vendor/re"
+    ]
+    ~f:(Topdirs.dir_directory);
+
+  let buf = Buffer.create (len + 1024) in
+  let ppf = Format.formatter_of_buffer buf in
+  List.iter chunks ~f:(fun (pos, s) ->
+    Format.fprintf ppf "%s[%%%%expect{|@." s;
+    let lexbuf = Lexing.from_string s in
+    lexbuf.lex_curr_p <- pos;
+    let phrases = !Toploop.parse_use_file lexbuf in
+    List.iter phrases ~f:(fun phr ->
+      ignore (Toploop.execute_phrase true ppf phr : bool));
+    Format.fprintf ppf "@?|}]@.");
+  let res = Buffer.contents buf in
+
+  let corrected_fn = fn ^ ".corrected" in
+  (* Temporary hack: *)
+  Sys.chdir "../..";
+  if txt <> res then begin
+    let oc = open_out_bin corrected_fn in
+    output_string oc res;
+    close_out oc;
+    Print_diff.print () ~file1:fn ~file2:corrected_fn;
+    exit 1
+  end else begin
+    if Sys.file_exists corrected_fn then Sys.remove corrected_fn;
+    exit 0
+  end
+
+let () =
+  try
+    main ()
+  with exn ->
+    Location.report_exception Format.err_formatter exn;
+    exit 1
+}
diff --git a/test/expect-tests/findlib-db/bar/META b/test/expect-tests/findlib-db/bar/META
new file mode 100644
index 00000000..e69de29b
diff --git a/test/expect-tests/findlib-db/baz/META b/test/expect-tests/findlib-db/baz/META
new file mode 100644
index 00000000..e69de29b
diff --git a/test/expect-tests/findlib-db/foo/META b/test/expect-tests/findlib-db/foo/META
new file mode 100644
index 00000000..e141935c
--- /dev/null
+++ b/test/expect-tests/findlib-db/foo/META
@@ -0,0 +1,2 @@
+requires = "bar"
+requires(ppx_driver) = "baz"
diff --git a/test/expect-tests/jbuild b/test/expect-tests/jbuild
new file mode 100644
index 00000000..08409113
--- /dev/null
+++ b/test/expect-tests/jbuild
@@ -0,0 +1,17 @@
+(jbuild_version 1)
+
+(executable
+ ((name expect_test)
+  (modules (expect_test))
+  (link_flags (-linkall))
+  (libraries (unix jbuilder compiler-libs.toplevel))))
+
+(ocamllex (expect_test))
+
+(alias
+ ((name runtest)
+  (deps (tests.mlt
+         (glob_files ${ROOT}/src/*.cmi)
+         (glob_files ${ROOT}/vendor/re/*.cmi)
+         (files_recursively_in findlib-db)))
+  (action (chdir ${ROOT} (run ${exe:expect_test.bc} ${<})))))
diff --git a/test/expect-tests/tests.mlt b/test/expect-tests/tests.mlt
new file mode 100644
index 00000000..77dff60f
--- /dev/null
+++ b/test/expect-tests/tests.mlt
@@ -0,0 +1,39 @@
+(* -*- tuareg -*- *)
+
+#warnings "-40";;
+
+open Jbuilder
+
+let print_pkg ppf pkg =
+  Format.fprintf ppf "<package:%s>" pkg.Findlib.name
+;;
+
+#install_printer print_pkg;;
+
+[%%expect{|
+val print_pkg : Format.formatter -> Jbuilder.Findlib.package -> unit = <fun>
+|}]
+
+let findlib =
+  let cwd = Path.absolute (Sys.getcwd ()) in
+    Findlib.create
+    ~stdlib_dir:cwd
+    ~path:[Path.relative cwd "test/expect-tests/findlib-db"]
+;;
+
+[%%expect{|
+val findlib : Jbuilder.Findlib.t = <abstr>
+|}]
+
+let pkg = Findlib.find_exn findlib ~required_by:[] "foo"
+
+[%%expect{|
+val pkg : Jbuilder.Findlib.package = <package:foo>
+|}]
+
+(* "foo" should depend on "baz" *)
+pkg.requires;;
+
+[%%expect{|
+- : Jbuilder.Findlib.package list = [<package:bar>]
+|}]
diff --git a/test/expect-tests/toplevel.ml b/test/expect-tests/toplevel.ml
new file mode 100644
index 00000000..8dcc82bb
--- /dev/null
+++ b/test/expect-tests/toplevel.ml
@@ -0,0 +1 @@
+Topmain.main ()