diff --git a/AUTHORS.adoc b/AUTHORS.adoc
index 5d6d131c6..56dba7428 100644
--- a/AUTHORS.adoc
+++ b/AUTHORS.adoc
@@ -25,3 +25,5 @@
 - Fabian Hemmer (copy)
 - Maciej Woś (@lostman)
 - Orbifx (Stavros Polymenis)
+- Rand (@rand00)
+- Dave Aitken (@actionshrimp)
diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index aa9a6e2ef..7e766c849 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -10,7 +10,7 @@
     by `include CCMonomorphic` in `Containers` module
   * Shadow the physical equality operator
   * Shadow polymorphic functions in `CCList`
-- rename `print` to `pp` for Format printers (closes #153)
+- rename `print` to `pp` for Format printers (closes #153, #181)
 - remove `CCFlatHashtbl`
 
 === others
@@ -22,6 +22,17 @@
 - Avoid uses of the polymorphic operators
 - Add a `CCMonomorphic` module shipped into a `containers.monomorphic` library
 - make complexity of `Array.lookup` explicit (closes #174)
+- add `CCFormat.lazy_{or,force}` for printing thunks
+- now that ocaml >= 4.02 is required, use `Format.pp_print_text` directly
+- add `CCHeap.delete_{one,all}`
+- add `CCList.tail_opt`
+
+
+- remove qtest makefile and use a script instead
+- add many tests
+- fix bug in `CCRAL.drop` (see #184)
+- `CCFormat`: fix support of unrecognized styles
+- fix bug: don't reverse twice in `CCList.repeat`
 
 == 1.5.1, 1.5.2
 
diff --git a/Makefile b/Makefile
index 1d9c7cb65..e925f0989 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ build:
 	jbuilder build @install
 
 test: build
-	jbuilder runtest --no-buffer
+	jbuilder runtest --no-buffer --force
 
 clean:
 	jbuilder clean
@@ -28,6 +28,12 @@ update_next_tag:
 	sed -i "s/NEXT_VERSION/$(VERSION)/g" $(wildcard src/**/*.ml) $(wildcard src/**/*.mli)
 	sed -i "s/NEXT_RELEASE/$(VERSION)/g" $(wildcard src/**/*.ml) $(wildcard src/**/*.mli)
 
+release: update_next_tag
+	@echo "release version $(VERSION)..."
+	git tag -f $(VERSION) ; git push origin :$(VERSION) ; git push origin $(VERSION)
+	opam publish prepare https://github.com/c-cube/qcheck/archive/$(VERSION).tar.gz
+	@echo "review the release, then type 'opam publish submit qcheck.$(VERSION)/'"
+
 watch:
 	while find src/ benchs/ -print0 | xargs -0 inotifywait -e delete_self -e modify ; do \
 		echo "============ at `date` ==========" ; \
diff --git a/README.adoc b/README.adoc
index a1468a936..6df889c97 100644
--- a/README.adoc
+++ b/README.adoc
@@ -484,7 +484,7 @@ Beforehand, check `grep deprecated -r src` to see whether some functions
 can be removed.
 
 . `make test`
-. update version in `_oasis`
+. update version in `containers.opam`
 . `make update_next_tag` (to update `@since` comments; be careful not to change symlinks)
 . check status of modules (`{b status: foo}`) and update if required;
    removed deprecated functions, etc.
@@ -492,8 +492,7 @@ can be removed.
 . commit the changes
 . `git checkout stable`
 . `git merge master`
-. `oasis setup; make test doc`
-. update `opam` (the version field; remove `oasis` in deps)
+. `make test doc`
 . tag, and push both to github
 . `opam pin add containers https://github.com/c-cube/ocaml-containers.git#<release>`
 . new opam package: `opam publish prepare; opam publish submit`
diff --git a/containers.opam b/containers.opam
index ace182e29..21bfedc7d 100644
--- a/containers.opam
+++ b/containers.opam
@@ -1,13 +1,13 @@
 opam-version: "1.2"
 name: "containers"
-version: "2.0+alpha2"
+version: "2.0"
 author: "Simon Cruanes"
 maintainer: "simon.cruanes.2007@m4x.org"
 build: [
     ["jbuilder" "build" "-p" name "-j" jobs]
 ]
 build-doc: [ "jbuilder" "build" "@doc" ]
-build-test: [ "jbuilder" "runtest" ]
+build-test: [ "jbuilder" "runtest" "-p" name "-j" jobs]
 depends: [
   "jbuilder" {build}
   "result"
@@ -18,6 +18,8 @@ depopts: [
   "qtest" { test }
   "qcheck" { test }
   "oUnit" { test }
+  "sequence" { test }
+  "gen" { test }
   "odoc" { doc }
 ]
 conflicts: [
@@ -37,5 +39,5 @@ These changes belong to 3 categories:
 - make most optional arguments relying on polymorphic operators mandatory
 - improve consistency of printers
 
-changelog: https://github.com/c-cube/ocaml-containers/blob/2.0+alpha1/CHANGELOG.adoc"
+changelog: https://github.com/c-cube/ocaml-containers/blob/2.0/CHANGELOG.adoc"
 ]
diff --git a/qtest/jbuild b/qtest/jbuild
index 8a027a969..8f48e6862 100644
--- a/qtest/jbuild
+++ b/qtest/jbuild
@@ -6,7 +6,7 @@
 
 (rule
   ((targets (run_qtest.ml))
-   (deps (make.bc))
+   (deps (make.bc (files_recursively_in ../src)))
    ;(libraries (qtest qcheck))
    (action
      (run ./make.bc -target ${@}))
diff --git a/src/core/CCArray.mli b/src/core/CCArray.mli
index 4fe5d32de..46784348a 100644
--- a/src/core/CCArray.mli
+++ b/src/core/CCArray.mli
@@ -222,7 +222,9 @@ val random_choose : 'a t -> 'a random_gen
     @raise Not_found if the array/slice is empty. *)
 
 val to_seq : 'a t -> 'a sequence
-(** Return a [sequence] of the elements of an array. *)
+(** Return a [sequence] of the elements of an array.
+    The input array is shared with the sequence and modifications of it will result
+    in modification of the sequence. *)
 
 val to_gen : 'a t -> 'a gen
 (** Return a [gen] of the elements of an array. *)
diff --git a/src/core/CCFormat.ml b/src/core/CCFormat.ml
index 965ff9edf..d01f3ad9e 100644
--- a/src/core/CCFormat.ml
+++ b/src/core/CCFormat.ml
@@ -46,35 +46,7 @@ let newline = Format.pp_force_newline
 let substring out (s,i,len): unit =
   string out (String.sub s i len)
 
-let text out (s:string): unit =
-  let len = String.length s in
-  let i = ref 0 in
-  let search_ c =
-    try Some (String.index_from s !i c) with Not_found -> None
-  in
-  while !i < len do
-    let j_newline = search_ '\n' in
-    let j_space = search_ ' ' in
-    let on_newline j =
-      substring out (s, !i, j - !i);
-      newline out ();
-      i := j + 1
-    and on_space j =
-      substring out (s, !i, j - !i);
-      Format.pp_print_space out ();
-      i := j + 1
-    in
-    begin match j_newline, j_space with
-      | None, None ->
-        (* done *)
-        substring out (s, !i, len - !i);
-        i := len
-      | Some j, None -> on_newline j
-      | None, Some j -> on_space j
-      | Some j1, Some j2 ->
-        if j1<j2 then on_newline j1 else on_space j2
-    end
-  done
+let text = Format.pp_print_text
 
 (*$= & ~printer:(fun s->CCFormat.sprintf "%S" s)
   "a\nb\nc" (sprintf_no_color "@[<v>%a@]%!" text "a b c")
@@ -161,6 +133,11 @@ let some pp out = function
   | None -> ()
   | Some x -> pp out x
 
+let lazy_force pp out (lazy x) = pp out x
+
+let lazy_or ?(default=return "<lazy>") pp out x =
+  if Lazy.is_val x then pp out (Lazy.force x) else default out ()
+
 (** {2 IO} *)
 
 let output fmt pp x = pp fmt x
@@ -266,6 +243,8 @@ let ansi_l_to_str_ = function
     Buffer.add_string buf "m";
     Buffer.contents buf
 
+exception No_such_style
+
 (* parse a tag *)
 let style_of_tag_ s = match String.trim s with
   | "reset" -> [`Reset]
@@ -286,7 +265,7 @@ let style_of_tag_ s = match String.trim s with
   | "Magenta" -> [`FG `Magenta; `Bold]
   | "Cyan" -> [`FG `Cyan; `Bold]
   | "White" -> [`FG `White; `Bold]
-  | s -> failwith ("unknown style: " ^ s)
+  | _ -> raise No_such_style
 
 let color_enabled = ref false
 
@@ -296,20 +275,21 @@ let mark_open_tag st ~or_else s =
     let style = style_of_tag_ s in
     Stack.push style st;
     if !color_enabled then ansi_l_to_str_ style else ""
-  with Not_found -> or_else s
+  with No_such_style -> or_else s
 
 let mark_close_tag st ~or_else s =
-  try
-    let _ = style_of_tag_ s in (* check if it's indeed about color *)
-    let style =
-      try
-        ignore (Stack.pop st); (* pop current style (if well-scoped...) *)
-        Stack.top st (* look at previous style *)
-      with Stack.Empty ->
-        [`Reset]
-    in
-    if !color_enabled then ansi_l_to_str_ style else ""
-  with Not_found -> or_else s
+  (* check if it's indeed about color *)
+  match style_of_tag_ s with
+    | _ ->
+      let style =
+        try
+          ignore (Stack.pop st); (* pop current style (if well-scoped...) *)
+          Stack.top st (* look at previous style *)
+        with Stack.Empty ->
+          [`Reset]
+      in
+      if !color_enabled then ansi_l_to_str_ style else ""
+    | exception No_such_style -> or_else s
 
 (* add color handling to formatter [ppf] *)
 let set_color_tag_handling ppf =
@@ -411,6 +391,10 @@ let ksprintf ~f fmt =
     (fun _ -> Format.pp_print_flush out (); f (Buffer.contents buf))
     out fmt
 
+(*$= & ~printer:CCFormat.(to_string (opt string))
+  (Some "hello world") \
+    (ksprintf "hello %a" CCFormat.string "world" ~f:(fun s -> Some s))
+*)
 
 module Dump = struct
   type 'a t = 'a printer
diff --git a/src/core/CCFormat.mli b/src/core/CCFormat.mli
index 6430bc939..8b2e5ffdd 100644
--- a/src/core/CCFormat.mli
+++ b/src/core/CCFormat.mli
@@ -129,6 +129,15 @@ val some : 'a printer -> 'a option printer
     @since 1.0
 *)
 
+val lazy_force : 'a printer -> 'a lazy_t printer
+(** [lazy_force pp out x] forces [x] and prints the result with [pp]
+    @since 2.0 *)
+
+val lazy_or : ?default:unit printer -> 'a printer -> 'a lazy_t printer
+(** [lazy_or ?default pp out x] prints [default] if [x] is not
+    evaluated yet, or uses [pp] otherwise
+    @since 2.0 *)
+
 (** {2 ANSI codes}
 
     Use ANSI escape codes https://en.wikipedia.org/wiki/ANSI_escape_code
@@ -271,11 +280,6 @@ val ksprintf :
     and then calls [f] on the resulting string.
     @since 0.14 *)
 
-(*$= & ~printer:CCFormat.(to_string (opt string))
-  (Some "hello world") \
-    (ksprintf "hello %a" CCFormat.string "world" ~f:(fun s -> Some s))
-*)
-
 val to_file : string -> ('a, t, unit, unit) format4 -> 'a
 (** Print to the given file. *)
 
diff --git a/src/core/CCHashtbl.mli b/src/core/CCHashtbl.mli
index 31c28970b..c4f712f49 100644
--- a/src/core/CCHashtbl.mli
+++ b/src/core/CCHashtbl.mli
@@ -31,6 +31,7 @@ module Poly : sig
 
   val keys_list : ('a, 'b) Hashtbl.t -> 'a list
   (** [keys_list t] is the list of keys in [t].
+      If the key is in the Hashtable multiple times, all occurrences will be returned.
       @since 0.8 *)
 
   val values_list : ('a, 'b) Hashtbl.t -> 'b list
@@ -150,6 +151,7 @@ module type S = sig
 
   val keys_list : _ t -> key list
   (** [keys_list t] is the list of keys in [t].
+      If the key is in the Hashtable multiple times, all occurrences will be returned.
       @since 0.8 *)
 
   val values_list : 'a t -> 'a list
diff --git a/src/core/CCHeap.mli b/src/core/CCHeap.mli
index 6606c76ee..cb53ddd84 100644
--- a/src/core/CCHeap.mli
+++ b/src/core/CCHeap.mli
@@ -97,13 +97,13 @@ module type S = sig
       @since 0.16 *)
 
   val of_list : elt list -> t
-  (** [of_list l] is [add_list empty l]. *)
+  (** [of_list l] is [add_list empty l]. Complexity: [O(n log n)]. *)
 
   val add_seq : t -> elt sequence -> t (** @since 0.16 *)
   (** Similar to {!add_list}. *)
 
   val of_seq : elt sequence -> t
-  (** Build a heap from a given [sequence]. *)
+  (** Build a heap from a given [sequence]. Complexity: [O(n log n)]. *)
 
   val to_seq : t -> elt sequence
   (** Return a [sequence] of the elements of the heap. *)
@@ -115,7 +115,7 @@ module type S = sig
   val add_klist : t -> elt klist -> t (** @since 0.16 *)
 
   val of_klist : elt klist -> t
-  (** Build a heap from a given [klist]. *)
+  (** Build a heap from a given [klist]. Complexity: [O(n log n)]. *)
 
   val to_klist : t -> elt klist
   (** Return a [klist] of the elements of the heap. *)
@@ -123,7 +123,7 @@ module type S = sig
   val add_gen : t -> elt gen -> t (** @since 0.16 *)
 
   val of_gen : elt gen -> t
-  (** Build a heap from a given [gen]. *)
+  (** Build a heap from a given [gen]. Complexity: [O(n log n)]. *)
 
   val to_gen : t -> elt gen
   (** Return a [gen] of the elements of the heap. *)
diff --git a/src/core/CCList.ml b/src/core/CCList.ml
index 3da6407f0..82291ba32 100644
--- a/src/core/CCList.ml
+++ b/src/core/CCList.ml
@@ -620,6 +620,9 @@ let sorted_insert ~cmp ?(uniq=false) x l =
   aux cmp uniq x [] l
 
 (*$Q
+    Q.(pair small_int (list small_int)) (fun (x,l) -> \
+      let l = List.sort Pervasives.compare l in \
+      is_sorted ~cmp:CCInt.compare (sorted_insert ~cmp:CCInt.compare x l))
     Q.(pair small_int (list small_int)) (fun (x,l) -> \
       let l = List.sort Pervasives.compare l in \
       is_sorted ~cmp:CCInt.compare (sorted_insert ~cmp:CCInt.compare ~uniq:true x l))
@@ -1253,11 +1256,21 @@ let replicate i x =
     else aux (x::acc) (i-1)
   in aux [] i
 
+
+(*$T
+  repeat 2 [1;2;3] = [1;2;3;1;2;3]
+*)
+
+(*$Q
+  Q.(pair small_int (small_list int)) (fun (n,l) -> \
+    if n>0 then repeat n l = flat_map (fun _ -> l) (1--n) \
+    else Q.assume_fail())
+*)
+
 let repeat i l =
-  let l' = List.rev l in
   let rec aux acc i =
     if i = 0 then List.rev acc
-    else aux (List.rev_append l' acc) (i-1)
+    else aux (List.rev_append l acc) (i-1)
   in aux [] i
 
 module Assoc = struct
diff --git a/src/core/CCList.mli b/src/core/CCList.mli
index 58041c2fe..b80bf76ad 100644
--- a/src/core/CCList.mli
+++ b/src/core/CCList.mli
@@ -340,12 +340,6 @@ val sorted_insert : cmp:('a -> 'a -> int) -> ?uniq:bool -> 'a -> 'a list -> 'a l
       [x] is not duplicated. Default [false] ([x] will be inserted in any case).
     @since 0.17 *)
 
-(*$Q
-    Q.(pair small_int (list small_int)) (fun (x,l) -> \
-      let l = List.sort Pervasives.compare l in \
-      is_sorted ~cmp:CCInt.compare (sorted_insert ~cmp:CCInt.compare x l))
-*)
-
 val uniq_succ : eq:('a -> 'a -> bool) -> 'a list -> 'a list
 (** [uniq_succ l] removes duplicate elements that occur one next to the other.
     Examples:
@@ -376,7 +370,7 @@ val iteri2 : (int -> 'a -> 'b -> unit) -> 'a t -> 'b t -> unit
     @since 2.0 *)
 
 val foldi : ('b -> int -> 'a -> 'b) -> 'b -> 'a t -> 'b
-(** Like [fold] but it also passes in the index of each element to the folded function. *)
+(** Like [fold] but it also passes in the index of each element to the folded function. Tail-recursive. *)
 
 val foldi2 : ('c -> int -> 'a -> 'b -> 'c) -> 'c -> 'a t -> 'b t -> 'c
 (** Fold on two lists, with index.
@@ -596,19 +590,22 @@ val to_seq : 'a t -> 'a sequence
 (** Return a [sequence] of the elements of the list. *)
 
 val of_seq : 'a sequence -> 'a t
-(** Build a list from a given [sequence]. *)
+(** Build a list from a given [sequence].
+    In the result, elements appear in the same order as they did in the source [sequence]. *)
 
 val to_gen : 'a t -> 'a gen
 (** Return a [gen] of the elements of the list. *)
 
 val of_gen : 'a gen -> 'a t
-(** Build a list from a given [gen]. *)
+(** Build a list from a given [gen].
+    In the result, elements appear in the same order as they did in the source [gen]. *)
 
 val to_klist : 'a t -> 'a klist
 (** Return a [klist] of the elements of the list. *)
 
 val of_klist : 'a klist -> 'a t
-(** Build a list from a given [klist]. *)
+(** Build a list from a given [klist].
+    In the result, elements appear in the same order as they did in the source [klist]. *)
 
 (** {2 Infix Operators}
     It is convenient to {!open CCList.Infix} to access the infix operators
@@ -646,5 +643,3 @@ end
 val pp : ?start:string -> ?stop:string -> ?sep:string ->
   'a printer -> 'a t printer
 (** Print the contents of a list. *)
-
-(** {2 Lists of pairs} *)
diff --git a/src/core/CCListLabels.mli b/src/core/CCListLabels.mli
index e0618a42b..6477295ec 100644
--- a/src/core/CCListLabels.mli
+++ b/src/core/CCListLabels.mli
@@ -232,12 +232,6 @@ val sorted_insert : cmp:('a -> 'a -> int) -> ?uniq:bool -> 'a -> 'a list -> 'a l
       [x] is not duplicated. Default [false] ([x] will be inserted in any case).
     @since 0.17 *)
 
-(*$Q
-    Q.(pair small_int (list small_int)) (fun (x,l) -> \
-      let l = List.sort Pervasives.compare l in \
-      is_sorted (sorted_insert x l))
-*)
-
 val uniq_succ : eq:('a -> 'a -> bool) -> 'a list -> 'a list
 (** [uniq_succ l] removes duplicate elements that occur one next to the other.
     Examples:
@@ -263,7 +257,7 @@ val iteri : f:(int -> 'a -> unit) -> 'a t -> unit
     itself as second argument. *)
 
 val foldi : f:('b -> int -> 'a -> 'b) -> init:'b -> 'a t -> 'b
-(** Like [fold] but it also passes in the index of each element to the folded function. *)
+(** Like [fold] but it also passes in the index of each element to the folded function. Tail-recursive. *)
 
 val get_at_idx : int -> 'a t -> 'a option
 (** Get by index in the list.
diff --git a/src/core/CCParse.ml b/src/core/CCParse.ml
index b66d0e6ab..2570a5125 100644
--- a/src/core/CCParse.ml
+++ b/src/core/CCParse.ml
@@ -3,6 +3,103 @@
 
 (** {1 Very Simple Parser Combinators} *)
 
+(*$inject
+  module T = struct
+    type tree = L of int | N of tree * tree
+  end
+  open T
+  open Result
+
+  let mk_leaf x = L x
+  let mk_node x y = N(x,y)
+
+  let ptree = fix @@ fun self ->
+    skip_space *>
+    ( (try_ (char '(') *> (pure mk_node <*> self <*> self) <* char ')')
+      <|>
+      (U.int >|= mk_leaf) )
+
+  let ptree' = fix_memo @@ fun self ->
+    skip_space *>
+    ( (try_ (char '(') *> (pure mk_node <*> self <*> self) <* char ')')
+      <|>
+      (U.int >|= mk_leaf) )
+
+  let rec pptree = function
+    | N (a,b) -> Printf.sprintf "N (%s, %s)" (pptree a) (pptree b)
+    | L x -> Printf.sprintf "L %d" x
+
+  let errpptree = function
+    | Ok x -> "Ok " ^ pptree x
+    | Error s -> "Error " ^ s
+*)
+
+(*$= & ~printer:errpptree
+  (Ok (N (L 1, N (L 2, L 3)))) \
+    (parse_string ptree "(1 (2 3))" )
+  (Ok (N (N (L 1, L 2), N (L 3, N (L 4, L 5))))) \
+    (parse_string ptree "((1 2) (3 (4 5)))" )
+  (Ok (N (L 1, N (L 2, L 3)))) \
+    (parse_string ptree' "(1 (2 3))" )
+  (Ok (N (N (L 1, L 2), N (L 3, N (L 4, L 5))))) \
+    (parse_string ptree' "((1 2) (3 (4 5)))" )
+*)
+
+(*$R
+  let p = U.list ~sep:"," U.word in
+  let printer = function
+    | Ok l -> "Ok " ^ CCFormat.(to_string (list string)) l
+    | Error s -> "Error " ^ s
+  in
+  assert_equal ~printer
+    (Ok ["abc"; "de"; "hello"; "world"])
+    (parse_string p "[abc , de, hello ,world  ]");
+*)
+
+(*$R
+  let test n =
+    let p = CCParse.(U.list ~sep:"," U.int) in
+
+    let l = CCList.(1 -- n) in
+    let l_printed =
+      CCFormat.(to_string (within "[" "]" (list ~sep:(return ",") int))) l in
+
+    let l' = CCParse.parse_string_exn p l_printed in
+
+    assert_equal ~printer:Q.Print.(list int) l l'
+  in
+  test 100_000;
+  test 400_000;
+
+*)
+
+(*$R
+  let open CCParse.Infix in
+  let module P = CCParse in
+
+  let parens p = P.try_ (P.char '(') *> p <* P.char ')' in
+  let add = P.char '+' *> P.return (+) in
+  let sub = P.char '-' *> P.return (-) in
+  let mul = P.char '*' *> P.return ( * ) in
+  let div = P.char '/' *> P.return ( / ) in
+  let integer =
+  P.chars1_if (function '0'..'9'->true|_->false) >|= int_of_string in
+
+  let chainl1 e op =
+  P.fix (fun r ->
+    e >>= fun x -> P.try_ (op <*> P.return x <*> r) <|> P.return x) in
+
+  let expr : int P.t =
+  P.fix (fun expr ->
+    let factor = parens expr <|> integer in
+    let term = chainl1 factor (mul <|> div) in
+    chainl1 term (add <|> sub)) in
+
+  assert_equal (Ok 6) (P.parse_string expr "4*1+2");
+  assert_equal (Ok 12) (P.parse_string expr "4*(1+2)");
+  ()
+*)
+
 type 'a or_error = ('a, string) Result.result
 
 type line_num = int
diff --git a/src/core/CCParse.mli b/src/core/CCParse.mli
index 3ebf1961c..b18d35d07 100644
--- a/src/core/CCParse.mli
+++ b/src/core/CCParse.mli
@@ -48,104 +48,6 @@
 
 *)
 
-(*$inject
-  module T = struct
-    type tree = L of int | N of tree * tree
-  end
-  open T
-  open Result
-
-  let mk_leaf x = L x
-  let mk_node x y = N(x,y)
-
-  let ptree = fix @@ fun self ->
-    skip_space *>
-    ( (try_ (char '(') *> (pure mk_node <*> self <*> self) <* char ')')
-      <|>
-      (U.int >|= mk_leaf) )
-
-  let ptree' = fix_memo @@ fun self ->
-    skip_space *>
-    ( (try_ (char '(') *> (pure mk_node <*> self <*> self) <* char ')')
-      <|>
-      (U.int >|= mk_leaf) )
-
-  let rec pptree = function
-    | N (a,b) -> Printf.sprintf "N (%s, %s)" (pptree a) (pptree b)
-    | L x -> Printf.sprintf "L %d" x
-
-  let errpptree = function
-    | Ok x -> "Ok " ^ pptree x
-    | Error s -> "Error " ^ s
-*)
-
-(*$= & ~printer:errpptree
-  (Ok (N (L 1, N (L 2, L 3)))) \
-    (parse_string ptree "(1 (2 3))" )
-  (Ok (N (N (L 1, L 2), N (L 3, N (L 4, L 5))))) \
-    (parse_string ptree "((1 2) (3 (4 5)))" )
-  (Ok (N (L 1, N (L 2, L 3)))) \
-    (parse_string ptree' "(1 (2 3))" )
-  (Ok (N (N (L 1, L 2), N (L 3, N (L 4, L 5))))) \
-    (parse_string ptree' "((1 2) (3 (4 5)))" )
-*)
-
-(*$R
-  let p = U.list ~sep:"," U.word in
-  let printer = function
-    | Ok l -> "Ok " ^ CCFormat.(to_string (list string)) l
-    | Error s -> "Error " ^ s
-  in
-  assert_equal ~printer
-    (Ok ["abc"; "de"; "hello"; "world"])
-    (parse_string p "[abc , de, hello ,world  ]");
-*)
-
-(*$R
-  let test n =
-    let p = CCParse.(U.list ~sep:"," U.int) in
-
-    let l = CCList.(1 -- n) in
-    let l_printed =
-      CCFormat.(to_string (within "[" "]" (list ~sep:(return ",") int))) l in
-
-    let l' = CCParse.parse_string_exn p l_printed in
-
-    assert_equal ~printer:Q.Print.(list int) l l'
-  in
-  test 100_000;
-  test 400_000;
-
-*)
-
-(*$R
-  let open CCParse.Infix in
-  let module P = CCParse in
-
-  let parens p = P.try_ (P.char '(') *> p <* P.char ')' in
-  let add = P.char '+' *> P.return (+) in
-  let sub = P.char '-' *> P.return (-) in
-  let mul = P.char '*' *> P.return ( * ) in
-  let div = P.char '/' *> P.return ( / ) in
-  let integer =
-  P.chars1_if (function '0'..'9'->true|_->false) >|= int_of_string in
-
-  let chainl1 e op =
-  P.fix (fun r ->
-    e >>= fun x -> P.try_ (op <*> P.return x <*> r) <|> P.return x) in
-
-  let expr : int P.t =
-  P.fix (fun expr ->
-    let factor = parens expr <|> integer in
-    let term = chainl1 factor (mul <|> div) in
-    chainl1 term (add <|> sub)) in
-
-  assert_equal (Ok 6) (P.parse_string expr "4*1+2");
-  assert_equal (Ok 12) (P.parse_string expr "4*(1+2)");
-  ()
-*)
-
-
 type 'a or_error = ('a, string) Result.result
 
 type line_num = int
diff --git a/src/core/CCString.ml b/src/core/CCString.ml
index 219cd554a..11291efed 100644
--- a/src/core/CCString.ml
+++ b/src/core/CCString.ml
@@ -13,6 +13,11 @@ let init n f =
   let buf = Bytes.init n f in
   Bytes.unsafe_to_string buf
 
+(*$T
+  init 3 (fun i -> [|'a'; 'b'; 'c'|].(i)) = "abc"
+  init 0 (fun _ -> assert false) = ""
+*)
+
 let uppercase_ascii = String.map CCChar.uppercase_ascii
 
 let lowercase_ascii = String.map CCChar.lowercase_ascii
@@ -71,6 +76,23 @@ let rev s =
   let n = length s in
   init n (fun i -> s.[n-i-1])
 
+(*$Q
+  Q.printable_string (fun s -> s = rev (rev s))
+  Q.printable_string (fun s -> length s = length (rev s))
+*)
+
+(*$Q
+  Q.printable_string (fun s -> \
+    rev s = (to_list s |> List.rev |> of_list))
+  *)
+
+
+(*$=
+  "abc" (rev "cba")
+  "" (rev "")
+  " " (rev " ")
+*)
+
 let rec _to_list s acc i len =
   if len=0 then List.rev acc
   else _to_list s (s.[i]::acc) (i+1) (len-1)
@@ -259,6 +281,19 @@ let find ?(start=0) ~sub =
   let pattern = Find.compile sub in
   fun s -> Find.find ~start ~pattern s
 
+(*$= & ~printer:string_of_int
+  1 (find ~sub:"bc" "abcd")
+  ~-1 (find ~sub:"bc" "abd")
+  1 (find ~sub:"a" "_a_a_a_")
+  6 (find ~sub:"a" ~start:5 "a1a234a")
+*)
+
+(*$Q & ~count:10_000
+  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
+    let i = find ~sub:s2 s1 in \
+    i < 0 || String.sub s1 i (length s2) = s2)
+*)
+
 let find_all ?(start=0) ~sub =
   let pattern = Find.compile sub in
   fun s ->
@@ -278,12 +313,38 @@ let find_all_l ?start ~sub s =
   in
   aux [] (find_all ?start ~sub s)
 
+(*$= & ~printer:Q.Print.(list int)
+  [1; 6] (find_all_l ~sub:"bc" "abc aabc  aab")
+  [] (find_all_l ~sub:"bc" "abd")
+  [76] (find_all_l ~sub:"aaaaaa" \
+    "aabbaabbaaaaabbbbabababababbbbabbbabbaaababbbaaabaabbaabbaaaabbababaaaabbaabaaaaaabbbaaaabababaabaaabbaabaaaabbababbaabbaaabaabbabababbbaabababaaabaaababbbaaaabbbaabaaababbabaababbaabbaaaaabababbabaababbbaaabbabbabababaaaabaaababaaaaabbabbaabbabbbbbbbbbbbbbbaabbabbbbbabbaaabbabbbbabaaaaabbababbbaaaa")
+*)
+
 let mem ?start ~sub s = find ?start ~sub s >= 0
 
+(*$T
+   mem ~sub:"bc" "abcd"
+   not (mem ~sub:"a b" "abcd")
+*)
+
 let rfind ~sub =
   let pattern = Find.rcompile sub in
   fun s -> Find.rfind ~start:(String.length s-1) ~pattern s
 
+(*$= & ~printer:string_of_int
+  1 (rfind ~sub:"bc" "abcd")
+  ~-1 (rfind ~sub:"bc" "abd")
+  5 (rfind ~sub:"a" "_a_a_a_")
+  4 (rfind ~sub:"bc" "abcdbcd")
+  6 (rfind ~sub:"a" "a1a234a")
+*)
+
+(*$Q & ~count:10_000
+  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
+    let i = rfind ~sub:s2 s1 in \
+    i < 0 || String.sub s1 i (length s2) = s2)
+*)
+
 (* Replace substring [s.[pos]....s.[pos+len-1]] by [by] in [s] *)
 let replace_at_ ~pos ~len ~by s =
   let b = Buffer.create (length s + length by - len) in
@@ -321,6 +382,16 @@ let replace ?(which=`All) ~sub ~by s =
       done;
       Buffer.contents b
 
+(*$= & ~printer:CCFun.id
+  (replace ~which:`All ~sub:"a" ~by:"b" "abcdabcd") "bbcdbbcd"
+  (replace ~which:`Left ~sub:"a" ~by:"b" "abcdabcd") "bbcdabcd"
+  (replace ~which:`Right ~sub:"a" ~by:"b" "abcdabcd") "abcdbbcd"
+  (replace ~which:`All ~sub:"ab" ~by:"hello" "  abab cdabb a") \
+    "  hellohello cdhellob a"
+  (replace ~which:`Left ~sub:"ab" ~by:"nope" " a b c d ") " a b c d "
+  (replace ~sub:"a" ~by:"b" "1aa234a") "1bb234b"
+*)
+
 module Split = struct
   type drop_if_empty = {
     first: bool;
@@ -379,6 +450,12 @@ module Split = struct
 
   let list_cpy ?(drop=default_drop) ~by s = _mklist ~drop ~by s String.sub
 
+  (*$T
+    Split.list_cpy ~by:"," "aa,bb,cc" = ["aa"; "bb"; "cc"]
+    Split.list_cpy ~by:"--" "a--b----c--" = ["a"; "b"; ""; "c"; ""]
+    Split.list_cpy ~by:" " "hello  world aie" = ["hello"; ""; "world"; "aie"]
+  *)
+
   let _mkklist ~drop ~by s k =
     let by = Find.compile by in
     let rec make state () = match _split ~by s state with
@@ -414,6 +491,14 @@ module Split = struct
 
   let left ~by s = try Some (left_exn ~by s) with Not_found -> None
 
+  (*$T
+    Split.left ~by:" " "ab cde f g " = Some ("ab", "cde f g ")
+    Split.left ~by:"__" "a__c__e_f" = Some ("a", "c__e_f")
+    Split.left ~by:"_" "abcde" = None
+    Split.left ~by:"bb" "abbc" = Some ("a", "c")
+    Split.left ~by:"a_" "abcde" = None
+  *)
+
   let right_exn ~by s =
     let i = rfind ~sub:by s in
     if i = ~-1 then raise Not_found
@@ -422,11 +507,30 @@ module Split = struct
       String.sub s 0 i, String.sub s right (String.length s - right)
 
   let right ~by s = try Some (right_exn ~by s) with Not_found -> None
+
+  (*$T
+    Split.right ~by:" " "ab cde f g" = Some ("ab cde f", "g")
+    Split.right ~by:"__" "a__c__e_f" = Some ("a__c", "e_f")
+    Split.right ~by:"_" "abcde" = None
+    Split.right ~by:"a_" "abcde" = None
+  *)
+
 end
 
 let split_on_char c s: _ list =
   Split.list_cpy ~drop:Split.no_drop ~by:(String.make 1 c) s
 
+(*$= & ~printer:Q.Print.(list string)
+  ["a"; "few"; "words"; "from"; "our"; "sponsors"] \
+    (split_on_char ' ' "a few words from our sponsors")
+*)
+
+(*$Q
+  Q.(printable_string) (fun s -> \
+    let s = split_on_char ' ' s |> String.concat " " in \
+    s = (split_on_char ' ' s |> String.concat " "))
+*)
+
 let split ~by s = Split.list_cpy ~by s
 
 let compare_versions a b =
@@ -448,6 +552,20 @@ let compare_versions a b =
   in
   cmp_rec (Split.gen_cpy ~by:"." a) (Split.gen_cpy ~by:"." b)
 
+(*$T
+  compare_versions "0.1.3" "0.1" > 0
+  compare_versions "10.1" "2.0" > 0
+  compare_versions "0.1.alpha" "0.1" > 0
+  compare_versions "0.3.dev" "0.4" < 0
+  compare_versions "0.foo" "0.0" < 0
+  compare_versions "1.2.3.4" "01.2.4.3" < 0
+*)
+
+(*$Q
+  Q.(pair printable_string printable_string) (fun (a,b) -> \
+    CCOrd.equiv (compare_versions a b) (CCOrd.opp compare_versions b a))
+*)
+
 type nat_chunk =
   | NC_char of char
   | NC_int of int
@@ -486,6 +604,25 @@ let compare_natural a b =
   in
   cmp_rec (chunks a) (chunks b)
 
+(*$T
+  compare_natural "foo1" "foo2" < 0
+  compare_natural "foo11" "foo2" > 0
+  compare_natural "foo11" "foo11" = 0
+  compare_natural "foo011" "foo11" = 0
+  compare_natural "foo1a" "foo1b" < 0
+  compare_natural "foo1a1" "foo1a2" < 0
+  compare_natural "foo1a17" "foo1a2" > 0
+*)
+
+(*Q
+  (Q.pair printable_string printable_string) (fun (a,b) -> \
+    CCOrd.opp (compare_natural a b) = compare_natural b a)
+  (Q.printable_string) (fun a -> compare_natural a a = 0)
+  (Q.triple printable_string printable_string printable_string) (fun (a,b,c) -> \
+    if compare_natural a b < 0 && compare_natural b c < 0 \
+    then compare_natural a c < 0 else Q.assume_fail())
+*)
+
 let edit_distance s1 s2 =
   if length s1 = 0
   then length s2
@@ -518,6 +655,35 @@ let edit_distance s1 s2 =
     v1.(length s2)
   end
 
+(*$Q
+  Q.(string_of_size Gen.(0 -- 30)) (fun s -> \
+    edit_distance s s = 0)
+*)
+
+(* test that building a from s, and mutating one char of s, yields
+   a string s' that is accepted by a.
+
+   --> generate triples (s, i, c) where c is a char, s a non empty string
+   and i a valid index in s.
+*)
+
+(*$QR
+  (
+    let gen = Q.Gen.(
+      3 -- 10 >>= fun len ->
+      0 -- (len-1) >>= fun i ->
+      string_size (return len) >>= fun s ->
+      char >|= fun c -> (s,i,c)
+    ) in
+    let small (s,_,_) = String.length s in
+    Q.make ~small gen
+  )
+  (fun (s,i,c) ->
+    let s' = Bytes.of_string s in
+    Bytes.set s' i c;
+    edit_distance s (Bytes.to_string s') <= 1)
+*)
+
 let repeat s n =
   assert (n>=0);
   let len = String.length s in
@@ -536,6 +702,16 @@ let prefix ~pre s =
     check 0
   )
 
+(*$T
+  prefix ~pre:"aab" "aabcd"
+  not (prefix ~pre:"ab" "aabcd")
+  not (prefix ~pre:"abcd" "abc")
+  prefix ~pre:"abc" "abcde"
+  prefix ~pre:"" ""
+  prefix ~pre:"" "abc"
+  prefix ~pre:"abc" "abc"
+*)
+
 let suffix ~suf s =
   let len = String.length suf in
   if len > String.length s then false
@@ -549,6 +725,14 @@ let suffix ~suf s =
     check 0
   )
 
+(*$T
+  suffix ~suf:"cd" "abcd"
+  suffix ~suf:"" ""
+  suffix ~suf:"" "abc"
+  not (suffix ~suf:"cd" "abcde")
+  not (suffix ~suf:"abcd" "cd")
+*)
+
 let take n s =
   if n < String.length s
   then String.sub s 0 n
@@ -561,16 +745,34 @@ let drop n s =
 
 let take_drop n s = take n s, drop n s
 
+(*$=
+  ("ab", "cd") (take_drop 2 "abcd")
+  ("abc", "") (take_drop 3 "abc")
+  ("abc", "") (take_drop 5 "abc")
+*)
+
 let chop_suffix ~suf s =
   if suffix ~suf s
   then Some (String.sub s 0 (String.length s-String.length suf))
   else None
 
+(*$= & ~printer:Q.Print.(option string)
+  (Some "ab") (chop_suffix ~suf:"cd" "abcd")
+  None (chop_suffix ~suf:"cd" "abcde")
+  None (chop_suffix ~suf:"abcd" "cd")
+*)
+
 let chop_prefix ~pre s =
   if prefix ~pre s
   then Some (String.sub s (String.length pre) (String.length s-String.length pre))
   else None
 
+(*$= & ~printer:Q.Print.(option string)
+  (Some "cd") (chop_prefix ~pre:"aab" "aabcd")
+  None (chop_prefix ~pre:"ab" "aabcd")
+  None (chop_prefix ~pre:"abcd" "abc")
+*)
+
 let blit = String.blit
 
 let fold f acc s =
@@ -588,6 +790,15 @@ let pad ?(side=`Left) ?(c=' ') n s =
       | `Left -> init n (fun i -> if i < pad_len then c else s.[i-pad_len])
       | `Right -> init n (fun i -> if i < len_s then s.[i] else c)
 
+(*$= & ~printer:Q.Print.string
+  "  42" (pad 4 "42")
+  "0042" (pad ~c:'0' 4 "42")
+  "4200" (pad ~side:`Right ~c:'0' 4 "42")
+  "hello" (pad 4 "hello")
+  "aaa" (pad ~c:'a' 3 "")
+  "aaa" (pad ~side:`Right ~c:'a' 3 "")
+*)
+
 let _to_gen s i0 len =
   let i = ref i0 in
   fun () ->
@@ -639,6 +850,11 @@ let of_list l =
   List.iter (Buffer.add_char buf) l;
   Buffer.contents buf
 
+(*$T
+  of_list ['a'; 'b'; 'c'] = "abc"
+  of_list [] = ""
+*)
+
 let of_array a =
   init (Array.length a) (fun i -> a.(i))
 
@@ -649,6 +865,14 @@ let lines_gen s = Split.gen_cpy ~drop:{Split.first=false; last=true} ~by:"\n" s
 
 let lines s = Split.list_cpy ~drop:{Split.first=false; last=true} ~by:"\n" s
 
+(*$= & ~printer:Q.Print.(list @@ Printf.sprintf "%S")
+  ["ab"; "c"] (lines "ab\nc")
+  ["ab"; "c"] (lines "ab\nc\n")
+  [] (lines "")
+  [""] (lines "\n")
+  [""; "a"] (lines "\na")
+*)
+
 let concat_gen_buf ~sep g : Buffer.t =
   let b = Buffer.create 256 in
   let rec aux ~first () = match g () with
@@ -683,10 +907,32 @@ let unlines_gen g =
   Buffer.add_char buf '\n';
   Buffer.contents buf
 
+(*$= & ~printer:CCFun.id
+  "" (unlines [])
+  "ab\nc\n" (unlines ["ab"; "c"])
+*)
+
+(*$Q
+  Q.printable_string (fun s -> trim (unlines (lines s)) = trim s)
+  Q.printable_string (fun s -> trim (unlines_gen (lines_gen s)) = trim s)
+*)
+
+(*$Q
+  Q.(list string) (fun l -> \
+    let l = unlines l |> lines in \
+    l = (unlines l |> lines))
+*)
+
 let set s i c =
   if i<0 || i>= String.length s then invalid_arg "CCString.set";
   init (String.length s) (fun j -> if i=j then c else s.[j])
 
+(*$T
+  set "abcd" 1 '_' = "a_cd"
+  set "abcd" 0 '-' = "-bcd"
+  (try ignore (set "abc" 5 '_'); false with Invalid_argument _ -> true)
+*)
+
 let iter = String.iter
 
 let filter_map f s =
@@ -698,6 +944,11 @@ let filter_map f s =
     s;
   Buffer.contents buf
 
+(*$= & ~printer:Q.Print.string
+  "bcef" (filter_map \
+     (function 'c' -> None | c -> Some (Char.chr (Char.code c + 1))) "abcde")
+*)
+
 let filter f s =
   let buf = Buffer.create (String.length s) in
   iter
@@ -705,6 +956,14 @@ let filter f s =
     s;
   Buffer.contents buf
 
+(*$= & ~printer:Q.Print.string
+  "abde" (filter (function 'c' -> false | _ -> true) "abcdec")
+*)
+
+(*$Q
+  Q.printable_string (fun s -> filter (fun _ -> true) s = s)
+*)
+
 let flat_map ?sep f s =
   let buf = Buffer.create (String.length s) in
   iteri
@@ -743,6 +1002,24 @@ let rtrim s =
   while !i >= 0 && is_space_ (unsafe_get s !i) do decr i done;
   if !i < length s-1 then sub s 0 (!i+1) else s
 
+(*$= & ~printer:id
+  "abc " (ltrim " abc ")
+  " abc" (rtrim " abc ")
+*)
+
+(*$Q
+  Q.(printable_string) (fun s -> \
+    String.trim s = (s |> ltrim |> rtrim))
+  Q.(printable_string) (fun s -> ltrim s = ltrim (ltrim s))
+  Q.(printable_string) (fun s -> rtrim s = rtrim (rtrim s))
+  Q.(printable_string) (fun s -> \
+    let s' = ltrim s in \
+    if s'="" then Q.assume_fail() else s'.[0] <> ' ')
+  Q.(printable_string) (fun s -> \
+    let s' = rtrim s in \
+    if s'="" then Q.assume_fail() else s'.[String.length s'-1] <> ' ')
+*)
+
 let map2 f s1 s2 =
   if length s1 <> length s2 then invalid_arg "CCString.map2";
   init (String.length s1) (fun i -> f s1.[i] s2.[i])
@@ -783,6 +1060,18 @@ let equal_caseless s1 s2: bool =
     (fun c1 c2 -> CCChar.equal (CCChar.lowercase_ascii c1) (CCChar.lowercase_ascii c2))
     s1 s2
 
+(*$T
+  equal_caseless "foo" "FoO"
+  equal_caseless "helLo" "HEllO"
+*)
+
+(*$Q
+  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
+    equal_caseless s1 s2 = (lowercase_ascii s1=lowercase_ascii s2))
+  Q.(printable_string) (fun s -> equal_caseless s s)
+  Q.(printable_string) (fun s -> equal_caseless (uppercase_ascii s) s)
+*)
+
 let pp_buf buf s =
   Buffer.add_char buf '"';
   Buffer.add_string buf s;
@@ -824,6 +1113,36 @@ module Sub = struct
       else fold_rec f (f acc s.[i]) s (i+1) j
     in fold_rec f acc s i (i+len)
 
+  (*$T
+    let s = Sub.make "abcde" 1 3 in \
+      Sub.fold (fun acc x -> x::acc) [] s = ['d'; 'c'; 'b']
+    Sub.make "abcde" 1 3 |> Sub.copy = "bcd"
+    Sub.full "abcde" |> Sub.copy = "abcde"
+  *)
+
+  (*$T
+    let sub = Sub.make " abc " 1 ~len:3 in \
+    "\"abc\"" = (CCFormat.to_string Sub.pp sub)
+  *)
+
+  (*$= & ~printer:(String.make 1)
+    'b' Sub.(get (make "abc" 1 ~len:2) 0)
+    'c' Sub.(get (make "abc" 1 ~len:2) 1)
+  *)
+
+  (*$QR
+    Q.(printable_string_of_size Gen.(3--10)) (fun s ->
+      let open Sequence.Infix in
+      begin
+        (0 -- (length s-2)
+          >|= fun i -> i, Sub.make s i ~len:(length s-i))
+        >>= fun (i,sub) ->
+        (0 -- (Sub.length sub-1) >|= fun j -> i,j,sub)
+      end
+      |> Sequence.for_all
+        (fun (i,j,sub) -> Sub.get sub j = s.[i+j]))
+  *)
+
   let to_gen (s,i,len) = _to_gen s i len
   let to_seq (s,i,len) k =
     for i=i to i+len-1 do k s.[i] done
diff --git a/src/core/CCString.mli b/src/core/CCString.mli
index ad4e181fe..60de94938 100644
--- a/src/core/CCString.mli
+++ b/src/core/CCString.mli
@@ -78,26 +78,10 @@ val init : int -> (int -> char) -> string
 (** Analog to [Array.init].
     @since 0.3.3 *)
 
-(*$T
-  init 3 (fun i -> [|'a'; 'b'; 'c'|].(i)) = "abc"
-  init 0 (fun _ -> assert false) = ""
-*)
-
 val rev : string -> string
 (** [rev s] returns the reverse of [s].
     @since 0.17 *)
 
-(*$Q
-  Q.printable_string (fun s -> s = rev (rev s))
-  Q.printable_string (fun s -> length s = length (rev s))
-*)
-
-(*$=
-  "abc" (rev "cba")
-  "" (rev "")
-  " " (rev " ")
-*)
-
 val pad : ?side:[`Left|`Right] -> ?c:char -> int -> string -> string
 (** [pad n str] ensures that [str] is at least [n] bytes long,
     and pads it on the [side] with [c] if it's not the case.
@@ -105,15 +89,6 @@ val pad : ?side:[`Left|`Right] -> ?c:char -> int -> string -> string
     @param c the char used to pad (default: ' ').
     @since 0.17 *)
 
-(*$= & ~printer:Q.Print.string
-  "  42" (pad 4 "42")
-  "0042" (pad ~c:'0' 4 "42")
-  "4200" (pad ~side:`Right ~c:'0' 4 "42")
-  "hello" (pad 4 "hello")
-  "aaa" (pad ~c:'a' 3 "")
-  "aaa" (pad ~side:`Right ~c:'a' 3 "")
-*)
-
 val of_char : char -> string
 (** [of_char 'a'] is ["a"].
     @since 0.19 *)
@@ -133,30 +108,12 @@ val of_list : char list -> string
 val of_array : char array -> string
 (** Convert an array of characters to a string. *)
 
-(*$T
-  of_list ['a'; 'b'; 'c'] = "abc"
-  of_list [] = ""
-*)
-
 val to_array : string -> char array
 (** Return the array of characters contained in the string. *)
 
 val find : ?start:int -> sub:string -> string -> int
 (** Find [sub] in string, returns its first index or [-1]. *)
 
-(*$= & ~printer:string_of_int
-  1 (find ~sub:"bc" "abcd")
-  ~-1 (find ~sub:"bc" "abd")
-  1 (find ~sub:"a" "_a_a_a_")
-  6 (find ~sub:"a" ~start:5 "a1a234a")
-*)
-
-(*$Q & ~count:10_000
-  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
-    let i = find ~sub:s2 s1 in \
-    i < 0 || String.sub s1 i (length s2) = s2)
-*)
-
 val find_all : ?start:int -> sub:string -> string -> int gen
 (** [find_all ~sub s] finds all occurrences of [sub] in [s], even overlapping
     instances.
@@ -169,41 +126,15 @@ val find_all_l : ?start:int -> sub:string -> string -> int list
     @param start starting position in [s].
     @since 0.17 *)
 
-(*$= & ~printer:Q.Print.(list int)
-  [1; 6] (find_all_l ~sub:"bc" "abc aabc  aab")
-  [] (find_all_l ~sub:"bc" "abd")
-  [76] (find_all_l ~sub:"aaaaaa" \
-    "aabbaabbaaaaabbbbabababababbbbabbbabbaaababbbaaabaabbaabbaaaabbababaaaabbaabaaaaaabbbaaaabababaabaaabbaabaaaabbababbaabbaaabaabbabababbbaabababaaabaaababbbaaaabbbaabaaababbabaababbaabbaaaaabababbabaababbbaaabbabbabababaaaabaaababaaaaabbabbaabbabbbbbbbbbbbbbbaabbabbbbbabbaaabbabbbbabaaaaabbababbbaaaa")
-*)
-
 val mem : ?start:int -> sub:string -> string -> bool
 (** [mem ~sub s] is true iff [sub] is a substring of [s].
     @since 0.12 *)
 
-(*$T
-   mem ~sub:"bc" "abcd"
-   not (mem ~sub:"a b" "abcd")
-*)
-
 val rfind : sub:string -> string -> int
 (** Find [sub] in string from the right, returns its first index or [-1].
     Should only be used with very small [sub].
     @since 0.12 *)
 
-(*$= & ~printer:string_of_int
-  1 (rfind ~sub:"bc" "abcd")
-  ~-1 (rfind ~sub:"bc" "abd")
-  5 (rfind ~sub:"a" "_a_a_a_")
-  4 (rfind ~sub:"bc" "abcdbcd")
-  6 (rfind ~sub:"a" "a1a234a")
-*)
-
-(*$Q & ~count:10_000
-  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
-    let i = rfind ~sub:s2 s1 in \
-    i < 0 || String.sub s1 i (length s2) = s2)
-*)
-
 val replace : ?which:[`Left|`Right|`All] -> sub:string -> by:string -> string -> string
 (** [replace ~sub ~by s] replaces some occurrences of [sub] by [by] in [s].
     @param which decides whether the occurrences to replace are:
@@ -215,16 +146,6 @@ val replace : ?which:[`Left|`Right|`All] -> sub:string -> by:string -> string ->
     @raise Invalid_argument if [sub = ""].
     @since 0.14 *)
 
-(*$= & ~printer:CCFun.id
-  (replace ~which:`All ~sub:"a" ~by:"b" "abcdabcd") "bbcdbbcd"
-  (replace ~which:`Left ~sub:"a" ~by:"b" "abcdabcd") "bbcdabcd"
-  (replace ~which:`Right ~sub:"a" ~by:"b" "abcdabcd") "abcdbbcd"
-  (replace ~which:`All ~sub:"ab" ~by:"hello" "  abab cdabb a") \
-    "  hellohello cdhellob a"
-  (replace ~which:`Left ~sub:"ab" ~by:"nope" " a b c d ") " a b c d "
-  (replace ~sub:"a" ~by:"b" "1aa234a") "1bb234b"
-*)
-
 val is_sub : sub:string -> int -> string -> int -> len:int -> bool
 (** [is_sub ~sub i s j ~len] returns [true] iff the substring of
     [sub] starting at position [i] and of length [len] is a substring
@@ -236,50 +157,20 @@ val repeat : string -> int -> string
 val prefix : pre:string -> string -> bool
 (** [prefix ~pre s] returns [true] iff [pre] is a prefix of [s]. *)
 
-(*$T
-  prefix ~pre:"aab" "aabcd"
-  not (prefix ~pre:"ab" "aabcd")
-  not (prefix ~pre:"abcd" "abc")
-  prefix ~pre:"abc" "abcde"
-  prefix ~pre:"" ""
-  prefix ~pre:"" "abc"
-  prefix ~pre:"abc" "abc"
-*)
-
 val suffix : suf:string -> string -> bool
 (** [suffix ~suf s] returns [true] iff [suf] is a suffix of [s].
     @since 0.7 *)
 
-(*$T
-  suffix ~suf:"cd" "abcd"
-  suffix ~suf:"" ""
-  suffix ~suf:"" "abc"
-  not (suffix ~suf:"cd" "abcde")
-  not (suffix ~suf:"abcd" "cd")
-*)
-
 val chop_prefix : pre:string -> string -> string option
 (** [chop_prefix ~pre s] removes [pre] from [s] if [pre] really is a prefix
     of [s], returns [None] otherwise.
     @since 0.17 *)
 
-(*$= & ~printer:Q.Print.(option string)
-  (Some "cd") (chop_prefix ~pre:"aab" "aabcd")
-  None (chop_prefix ~pre:"ab" "aabcd")
-  None (chop_prefix ~pre:"abcd" "abc")
-*)
-
 val chop_suffix : suf:string -> string -> string option
 (** [chop_suffix ~suf s] removes [suf] from [s] if [suf] really is a suffix
     of [s], returns [None] otherwise.
     @since 0.17 *)
 
-(*$= & ~printer:Q.Print.(option string)
-  (Some "ab") (chop_suffix ~suf:"cd" "abcd")
-  None (chop_suffix ~suf:"cd" "abcde")
-  None (chop_suffix ~suf:"abcd" "cd")
-*)
-
 val take : int -> string -> string
 (** [take n s] keeps only the [n] first chars of [s].
     @since 0.17 *)
@@ -292,12 +183,6 @@ val take_drop : int -> string -> string * string
 (** [take_drop n s = take n s, drop n s].
     @since 0.17 *)
 
-(*$=
-  ("ab", "cd") (take_drop 2 "abcd")
-  ("abc", "") (take_drop 3 "abc")
-  ("abc", "") (take_drop 5 "abc")
-*)
-
 val lines : string -> string list
 (** [lines s] returns a list of the lines of [s] (splits along '\n').
     @since 0.10 *)
@@ -306,14 +191,6 @@ val lines_gen : string -> string gen
 (** [lines_gen s] returns a generator of the lines of [s] (splits along '\n').
     @since 0.10 *)
 
-(*$= & ~printer:Q.Print.(list @@ Printf.sprintf "%S")
-  ["ab"; "c"] (lines "ab\nc")
-  ["ab"; "c"] (lines "ab\nc\n")
-  [] (lines "")
-  [""] (lines "\n")
-  [""; "a"] (lines "\na")
-*)
-
 val concat_gen : sep:string -> string gen -> string
 (** [concat_gen ~sep g] concatenates all strings of [g], separated with [sep].
     @since 0.10 *)
@@ -326,34 +203,12 @@ val unlines_gen : string gen -> string
 (** [unlines_gen g] concatenates all strings of [g], separated with '\n'.
     @since 0.10 *)
 
-(*$= & ~printer:CCFun.id
-  "" (unlines [])
-  "ab\nc\n" (unlines ["ab"; "c"])
-*)
-
-(*$Q
-  Q.printable_string (fun s -> trim (unlines (lines s)) = trim s)
-  Q.printable_string (fun s -> trim (unlines_gen (lines_gen s)) = trim s)
-*)
-
-(*$Q
-  Q.(list string) (fun l -> \
-    let l = unlines l |> lines in \
-    l = (unlines l |> lines))
-*)
-
 val set : string -> int -> char -> string
 (** [set s i c] creates a new string which is a copy of [s], except
     for index [i], which becomes [c].
     @raise Invalid_argument if [i] is an invalid index.
     @since 0.12 *)
 
-(*$T
-  set "abcd" 1 '_' = "a_cd"
-  set "abcd" 0 '-' = "-bcd"
-  (try ignore (set "abc" 5 '_'); false with Invalid_argument _ -> true)
-*)
-
 val iter : (char -> unit) -> string -> unit
 (** Alias to {!String.iter}.
     @since 0.12 *)
@@ -376,23 +231,10 @@ val filter_map : (char -> char option) -> string -> string
     the corresponding element of [s] is discarded).
     @since 0.17 *)
 
-(*$= & ~printer:Q.Print.string
-  "bcef" (filter_map \
-     (function 'c' -> None | c -> Some (Char.chr (Char.code c + 1))) "abcde")
-*)
-
 val filter : (char -> bool) -> string -> string
 (** [filter f s] discards characters not satisfying [f].
     @since 0.17 *)
 
-(*$= & ~printer:Q.Print.string
-  "abde" (filter (function 'c' -> false | _ -> true) "abcdec")
-*)
-
-(*$Q
-  Q.printable_string (fun s -> filter (fun _ -> true) s = s)
-*)
-
 val flat_map : ?sep:string -> (char -> string) -> string -> string
 (** Map each chars to a string, then concatenates them all.
     @param sep optional separator between each generated string.
@@ -416,24 +258,6 @@ val rtrim : t -> t
 (** Trim space on the right (see {!String.trim} for more details).
     @since 1.2 *)
 
-(*$= & ~printer:id
-  "abc " (ltrim " abc ")
-  " abc" (rtrim " abc ")
-*)
-
-(*$Q
-  Q.(printable_string) (fun s -> \
-    String.trim s = (s |> ltrim |> rtrim))
-  Q.(printable_string) (fun s -> ltrim s = ltrim (ltrim s))
-  Q.(printable_string) (fun s -> rtrim s = rtrim (rtrim s))
-  Q.(printable_string) (fun s -> \
-    let s' = ltrim s in \
-    if s'="" then Q.assume_fail() else s'.[0] <> ' ')
-  Q.(printable_string) (fun s -> \
-    let s' = rtrim s in \
-    if s'="" then Q.assume_fail() else s'.[String.length s'-1] <> ' ')
-*)
-
 (** {2 Operations on 2 strings} *)
 
 val map2 : (char -> char -> char) -> string -> string -> string
@@ -487,18 +311,6 @@ val equal_caseless : string -> string -> bool
 (** Comparison without respect to {b ascii} lowercase.
     @since 1.2 *)
 
-(*$T
-  equal_caseless "foo" "FoO"
-  equal_caseless "helLo" "HEllO"
-*)
-
-(*$Q
-  Q.(pair printable_string printable_string) (fun (s1,s2) -> \
-    equal_caseless s1 s2 = (lowercase_ascii s1=lowercase_ascii s2))
-  Q.(printable_string) (fun s -> equal_caseless s s)
-  Q.(printable_string) (fun s -> equal_caseless (uppercase_ascii s) s)
-*)
-
 (** {2 Finding}
 
     A relatively efficient algorithm for finding sub-strings.
@@ -566,12 +378,6 @@ module Split : sig
 
   val list_cpy : ?drop:drop_if_empty -> by:string -> string -> string list
 
-  (*$T
-    Split.list_cpy ~by:"," "aa,bb,cc" = ["aa"; "bb"; "cc"]
-    Split.list_cpy ~by:"--" "a--b----c--" = ["a"; "b"; ""; "c"; ""]
-    Split.list_cpy ~by:" " "hello  world aie" = ["hello"; ""; "world"; "aie"]
-  *)
-
   val gen_cpy : ?drop:drop_if_empty -> by:string -> string -> string gen
 
   val seq_cpy : ?drop:drop_if_empty -> by:string -> string -> string sequence
@@ -588,14 +394,6 @@ module Split : sig
       @raise Not_found if [by] is not part of the string.
       @since 0.16 *)
 
-  (*$T
-    Split.left ~by:" " "ab cde f g " = Some ("ab", "cde f g ")
-    Split.left ~by:"__" "a__c__e_f" = Some ("a", "c__e_f")
-    Split.left ~by:"_" "abcde" = None
-    Split.left ~by:"bb" "abbc" = Some ("a", "c")
-    Split.left ~by:"a_" "abcde" = None
-  *)
-
   val right : by:string -> string -> (string * string) option
   (** Split on the first occurrence of [by] from the rightmost part of
       the string.
@@ -606,29 +404,12 @@ module Split : sig
       @raise Not_found if [by] is not part of the string.
       @since 0.16 *)
 
-  (*$T
-    Split.right ~by:" " "ab cde f g" = Some ("ab cde f", "g")
-    Split.right ~by:"__" "a__c__e_f" = Some ("a__c", "e_f")
-    Split.right ~by:"_" "abcde" = None
-    Split.right ~by:"a_" "abcde" = None
-  *)
 end
 
 val split_on_char : char -> string -> string list
 (** Split the string along the given char.
     @since 1.2 *)
 
-(*$= & ~printer:Q.Print.(list string)
-  ["a"; "few"; "words"; "from"; "our"; "sponsors"] \
-    (split_on_char ' ' "a few words from our sponsors")
-*)
-
-(*$Q
-  Q.(printable_string) (fun s -> \
-    let s = split_on_char ' ' s |> String.concat " " in \
-    s = (split_on_char ' ' s |> String.concat " "))
-*)
-
 val split : by:string -> string -> string list
 (** Alias to {!Split.list_cpy}.
     @since 1.2 *)
@@ -640,78 +421,16 @@ val compare_versions : string -> string -> int
     considering that numbers are above text.
     @since 0.13 *)
 
-(*$T
-  compare_versions "0.1.3" "0.1" > 0
-  compare_versions "10.1" "2.0" > 0
-  compare_versions "0.1.alpha" "0.1" > 0
-  compare_versions "0.3.dev" "0.4" < 0
-  compare_versions "0.foo" "0.0" < 0
-  compare_versions "1.2.3.4" "01.2.4.3" < 0
-*)
-
-(*$Q
-  Q.(pair printable_string printable_string) (fun (a,b) -> \
-    CCOrd.equiv (compare_versions a b) (CCOrd.opp compare_versions b a))
-*)
-
 val compare_natural : string -> string -> int
 (** Natural Sort Order, comparing chunks of digits as natural numbers.
     https://en.wikipedia.org/wiki/Natural_sort_order
     @since 1.3 *)
 
-(*$T
-  compare_natural "foo1" "foo2" < 0
-  compare_natural "foo11" "foo2" > 0
-  compare_natural "foo11" "foo11" = 0
-  compare_natural "foo011" "foo11" = 0
-  compare_natural "foo1a" "foo1b" < 0
-  compare_natural "foo1a1" "foo1a2" < 0
-  compare_natural "foo1a17" "foo1a2" > 0
-*)
-
-(*Q
-  (Q.pair printable_string printable_string) (fun (a,b) -> \
-    CCOrd.opp (compare_natural a b) = compare_natural b a)
-  (Q.printable_string) (fun a -> compare_natural a a = 0)
-  (Q.triple printable_string printable_string printable_string) (fun (a,b,c) -> \
-    if compare_natural a b < 0 && compare_natural b c < 0 \
-    then compare_natural a c < 0 else Q.assume_fail())
-*)
-
 val edit_distance : string -> string -> int
 (** Edition distance between two strings. This satisfies the classical
     distance axioms: it is always positive, symmetric, and satisfies
     the formula [distance a b + distance b c >= distance a c]. *)
 
-(*$Q
-  Q.(string_of_size Gen.(0 -- 30)) (fun s -> \
-    edit_distance s s = 0)
-*)
-
-(* test that building a from s, and mutating one char of s, yields
-   a string s' that is accepted by a.
-
-   --> generate triples (s, i, c) where c is a char, s a non empty string
-   and i a valid index in s.
-*)
-
-(*$QR
-  (
-    let gen = Q.Gen.(
-      3 -- 10 >>= fun len ->
-      0 -- (len-1) >>= fun i ->
-      string_size (return len) >>= fun s ->
-      char >|= fun c -> (s,i,c)
-    ) in
-    let small (s,_,_) = String.length s in
-    Q.make ~small gen
-  )
-  (fun (s,i,c) ->
-    let s' = Bytes.of_string s in
-    Bytes.set s' i c;
-    edit_distance s (Bytes.to_string s') <= 1)
-*)
-
 (** {2 Slices} A contiguous part of a string *)
 
 module Sub : sig
@@ -738,33 +457,4 @@ module Sub : sig
 
   include S with type t := t
 
-  (*$T
-    let s = Sub.make "abcde" 1 3 in \
-      Sub.fold (fun acc x -> x::acc) [] s = ['d'; 'c'; 'b']
-    Sub.make "abcde" 1 3 |> Sub.copy = "bcd"
-    Sub.full "abcde" |> Sub.copy = "abcde"
-  *)
-
-  (*$T
-    let sub = Sub.make " abc " 1 ~len:3 in \
-    "\"abc\"" = (CCFormat.to_string Sub.pp sub)
-  *)
-
-  (*$= & ~printer:(String.make 1)
-    'b' Sub.(get (make "abc" 1 ~len:2) 0)
-    'c' Sub.(get (make "abc" 1 ~len:2) 1)
-  *)
-
-  (*$QR
-    Q.(printable_string_of_size Gen.(3--10)) (fun s ->
-      let open Sequence.Infix in
-      begin
-        (0 -- (length s-2)
-          >|= fun i -> i, Sub.make s i ~len:(length s-i))
-        >>= fun (i,sub) ->
-        (0 -- (Sub.length sub-1) >|= fun j -> i,j,sub)
-      end
-      |> Sequence.for_all
-        (fun (i,j,sub) -> Sub.get sub j = s.[i+j]))
-  *)
 end
diff --git a/src/core/CCVector.mli b/src/core/CCVector.mli
index e6ab05070..3b1f4f172 100644
--- a/src/core/CCVector.mli
+++ b/src/core/CCVector.mli
@@ -239,7 +239,7 @@ val (--^) : int -> int -> (int, 'mut) t
     @since 0.17 *)
 
 val of_array : 'a array -> ('a, 'mut) t
-(** [of_array a] returns a vector corresponding to the array [a]. *)
+(** [of_array a] returns a vector corresponding to the array [a]. Operates in [O(n)] time. *)
 
 val of_list : 'a list -> ('a, 'mut) t
 
diff --git a/src/core/META b/src/core/META
deleted file mode 100644
index d5c489691..000000000
--- a/src/core/META
+++ /dev/null
@@ -1,77 +0,0 @@
-# OASIS_START
-# DO NOT EDIT (digest: 6fc8b50f808e0788951f153fb45868c5)
-version = "1.5.2"
-description = "A modular standard library focused on data structures."
-requires = "bytes result"
-archive(byte) = "containers.cma"
-archive(byte, plugin) = "containers.cma"
-archive(native) = "containers.cmxa"
-archive(native, plugin) = "containers.cmxs"
-exists_if = "containers.cma"
-package "unix" (
- version = "1.5.2"
- description = "A modular standard library focused on data structures."
- requires = "bytes result unix"
- archive(byte) = "containers_unix.cma"
- archive(byte, plugin) = "containers_unix.cma"
- archive(native) = "containers_unix.cmxa"
- archive(native, plugin) = "containers_unix.cmxs"
- exists_if = "containers_unix.cma"
-)
-
-package "top" (
- version = "1.5.2"
- description = "A modular standard library focused on data structures."
- requires =
- "compiler-libs.common containers containers.data containers.unix containers.sexp containers.iter"
- archive(byte) = "containers_top.cma"
- archive(byte, plugin) = "containers_top.cma"
- archive(native) = "containers_top.cmxa"
- archive(native, plugin) = "containers_top.cmxs"
- exists_if = "containers_top.cma"
-)
-
-package "thread" (
- version = "1.5.2"
- description = "A modular standard library focused on data structures."
- requires = "containers threads"
- archive(byte) = "containers_thread.cma"
- archive(byte, plugin) = "containers_thread.cma"
- archive(native) = "containers_thread.cmxa"
- archive(native, plugin) = "containers_thread.cmxs"
- exists_if = "containers_thread.cma"
-)
-
-package "sexp" (
- version = "1.5.2"
- description = "A modular standard library focused on data structures."
- requires = "bytes result"
- archive(byte) = "containers_sexp.cma"
- archive(byte, plugin) = "containers_sexp.cma"
- archive(native) = "containers_sexp.cmxa"
- archive(native, plugin) = "containers_sexp.cmxs"
- exists_if = "containers_sexp.cma"
-)
-
-package "iter" (
- version = "1.5.2"
- description = "A modular standard library focused on data structures."
- archive(byte) = "containers_iter.cma"
- archive(byte, plugin) = "containers_iter.cma"
- archive(native) = "containers_iter.cmxa"
- archive(native, plugin) = "containers_iter.cmxs"
- exists_if = "containers_iter.cma"
-)
-
-package "data" (
- version = "1.5.2"
- description = "A modular standard library focused on data structures."
- requires = "bytes"
- archive(byte) = "containers_data.cma"
- archive(byte, plugin) = "containers_data.cma"
- archive(native) = "containers_data.cmxa"
- archive(native, plugin) = "containers_data.cmxs"
- exists_if = "containers_data.cma"
-)
-# OASIS_STOP
-
diff --git a/src/data/CCRAL.ml b/src/data/CCRAL.ml
index f025bf53a..f72cb7c34 100644
--- a/src/data/CCRAL.ml
+++ b/src/data/CCRAL.ml
@@ -257,6 +257,13 @@ let flat_map f l =
       append l acc
     )
 
+(*$Q
+  Q.(pair (fun1 Observable.int (small_list int)) (small_list int)) (fun (f,l) -> \
+    let f x = Q.Fn.apply f x in \
+    let f' x = f x |> of_list in \
+    of_list l |> flat_map f' |> to_list = CCList.(flat_map f l))
+*)
+
 let flatten l = fold_rev ~f:(fun acc l -> append l acc) ~x:empty l
 
 (*$T
@@ -264,6 +271,11 @@ let flatten l = fold_rev ~f:(fun acc l -> append l acc) ~x:empty l
     of_list [1;2;3;]
 *)
 
+(*$Q
+  Q.(small_list (small_list int)) (fun l -> \
+    of_list l |> map ~f:of_list |> flatten |> to_list = CCList.flatten l)
+*)
+
 let app funs l =
   fold_rev ~x:empty funs
     ~f:(fun acc f ->
@@ -307,6 +319,11 @@ and take_tree_ ~size n t = match t with
   take 0 (of_list CCList.(1--10)) |> to_list = []
 *)
 
+(*$Q
+  Q.(pair small_int (list int)) (fun (n,l) -> \
+    of_list l |> take n |> to_list = CCList.take n l)
+*)
+
 let take_while ~f l =
   (* st: stack of subtrees *)
   let rec aux p st = match st with
@@ -323,24 +340,49 @@ let take_while ~f l =
   Q.(list int) (fun l -> \
     let f x = x mod 7 <> 0 in \
     of_list l |> take_while ~f |> to_list = CCList.take_while f l)
+  Q.(pair (fun1 Observable.int bool) (list int)) (fun (f,l) -> \
+    let f x = Q.Fn.apply f x in \
+    of_list l |> take_while ~f |> to_list = CCList.take_while f l)
 *)
 
+(* drop [n < size] elements from [t] *)
+let rec drop_tree_ ~size n t tail = match t with
+  | _ when n=0 -> tail
+  | Leaf _ ->
+    assert (n=1);
+    tail
+  | Node (_,left,right) ->
+    if n=1 then append_tree_ left (append_tree_ right tail)
+    else (
+      assert (size mod 2 = 1);
+      let size_sub = size/2 in (* size of subtrees *)
+      let n = n-1 in
+      if n = size_sub then (
+        append_tree_ right tail (* drop element and left tree *)
+      ) else if n < size_sub then (
+        (* drop element and part of left tree *)
+        drop_tree_ ~size:size_sub n left (append_tree_ right tail)
+      ) else (
+        (* drop element, left tree, and part of right tree *)
+        drop_tree_ ~size:size_sub (n-size_sub) right tail
+      )
+    )
+
 let rec drop n l = match l with
   | _ when n=0 -> l
   | Nil -> Nil
   | Cons (size, t, tl) ->
     if n >= size then drop (n-size) tl
     else drop_tree_ ~size n t tl
-and drop_tree_ ~size n t tail = match t with
-  | _ when n=0 -> tail
-  | Leaf _ -> tail
-  | Node (_,l,r) ->
-    if n=1 then append_tree_ l (append_tree_ r tail)
-    else
-      let size' = size/2 in
-      if n-1 < size'
-      then drop_tree_ ~size:size' (n-1) l (append_tree_ r tail)
-      else drop_tree_ ~size:size' (n-1-size') r tail
+
+(*$T
+  of_list [1;2;3] |> drop 2 |> length = 1
+*)
+
+(*$Q
+  Q.(pair small_int (list int)) (fun (n,l) -> \
+    of_list l |> drop n |> to_list = CCList.drop n l)
+*)
 
 let drop_while ~f l =
   let rec aux p st = match st with
@@ -406,6 +448,12 @@ let repeat n l =
   in
   aux n l empty
 
+
+(*$Q
+  Q.(pair small_int (small_list int)) (fun (n,l) -> \
+    of_list l |> repeat n |> to_list = CCList.(repeat n l))
+*)
+
 let range i j =
   let rec aux i j acc =
     if i=j then cons i acc
diff --git a/src/data/CCRingBuffer.ml b/src/data/CCRingBuffer.ml
index af64a188a..7c2e88b7e 100644
--- a/src/data/CCRingBuffer.ml
+++ b/src/data/CCRingBuffer.ml
@@ -200,7 +200,7 @@ end
   open Q.Gen
   let g_char = map Char.chr (Char.code 'A' -- Char.code 'z')
   let g_str = string_size ~gen:g_char (0--10)
-  let a_str = {Q.string with Q.gen=g_str}
+  let a_str = Q.set_gen g_str Q.string
 *)
 
 module MakeFromArray(A:Array.S) : S with module Array = A = struct
diff --git a/src/data/CCZipper.ml b/src/data/CCZipper.ml
index 30d227d1c..ec7eb143e 100644
--- a/src/data/CCZipper.ml
+++ b/src/data/CCZipper.ml
@@ -11,6 +11,11 @@ let is_empty = function
   | [], [] -> true
   | _ -> false
 
+(*$T
+  (is_empty empty)
+  not ([42] |> make |> right |> is_empty)
+*)
+
 let to_list (l,r) = List.rev_append l r
 
 let to_rev_list (l,r) = List.rev_append r l
@@ -89,3 +94,9 @@ let drop_after (l, r) = match r with
   | x :: _ -> l, [x]
 
 let drop_after_and_focused (l, _) = l, []
+
+(*$=
+  ([1], [2]) (drop_after ([1], [2;3]))
+  ([1], []) (drop_after ([1], []))
+  ([1], []) (drop_after_and_focused ([1], [2;3]))
+*)
diff --git a/src/data/CCZipper.mli b/src/data/CCZipper.mli
index 763074ecb..9d3ea4aeb 100644
--- a/src/data/CCZipper.mli
+++ b/src/data/CCZipper.mli
@@ -15,11 +15,6 @@ val empty : 'a t
 val is_empty : _ t -> bool
 (** Empty zipper? Returns true iff the two lists are empty. *)
 
-(*$T
-  (is_empty empty)
-  not ([42] |> make |> right |> is_empty)
-*)
-
 val to_list : 'a t -> 'a list
 (** Convert the zipper back to a list.
     [to_list (l,r)] is [List.rev_append l r]. *)
@@ -79,9 +74,4 @@ val drop_after_and_focused : 'a t -> 'a t
 (** Drop every element on the "right" (calling {!right} then will do nothing),
     {i including} the focused element if it is present. *)
 
-(*$=
-  ([1], [2]) (drop_after ([1], [2;3]))
-  ([1], []) (drop_after ([1], []))
-  ([1], []) (drop_after_and_focused ([1], [2;3]))
-*)
 
diff --git a/src/unix/CCUnix.ml b/src/unix/CCUnix.ml
index 4d2b4d55a..905cd359f 100644
--- a/src/unix/CCUnix.ml
+++ b/src/unix/CCUnix.ml
@@ -50,6 +50,12 @@ let escape_str s =
     Buffer.contents buf
   ) else s
 
+(*$T
+  escape_str "foo" = "foo"
+  escape_str "foo bar" = "'foo bar'"
+  escape_str "fo'o b'ar" = "'fo'\\''o b'\\''ar'"
+*)
+
 let read_all ?(size=1024) ic =
   let buf = ref (Bytes.create size) in
   let len = ref 0 in
@@ -107,6 +113,12 @@ let call_full ?bufsize ?stdin ?env cmd =
         method errcode = int_of_process_status status
       end)
 
+(*$T
+  call_full ~stdin:(`Str "abc") "cat" |> stdout = "abc"
+  call_full "echo %s" (escape_str "a'b'c") |> stdout = "a'b'c\n"
+  call_full "echo %s" "a'b'c" |> stdout = "abc\n"
+*)
+
 let call ?bufsize ?stdin ?env cmd =
   call_full_inner ?bufsize ?stdin ?env cmd
     ~f:(fun (out,err,status) -> out, err, int_of_process_status status)
@@ -115,6 +127,12 @@ let call_stdout ?bufsize ?stdin ?env cmd =
   call_full_inner ?bufsize ?stdin ?env cmd
     ~f:(fun (out,_err,_status) -> out)
 
+(*$T
+  call_stdout ~stdin:(`Str "abc") "cat" = "abc"
+  call_stdout "echo %s" (escape_str "a'b'c") = "a'b'c\n"
+  call_stdout "echo %s" "a'b'c" = "abc\n"
+*)
+
 type line = string
 
 type async_call_result =
diff --git a/src/unix/CCUnix.mli b/src/unix/CCUnix.mli
index 938363397..77657dd44 100644
--- a/src/unix/CCUnix.mli
+++ b/src/unix/CCUnix.mli
@@ -16,12 +16,6 @@ type 'a gen = unit -> 'a option
 val escape_str : string -> string
 (** Escape a string so it can be a shell argument. *)
 
-(*$T
-  escape_str "foo" = "foo"
-  escape_str "foo bar" = "'foo bar'"
-  escape_str "fo'o b'ar" = "'fo'\\''o b'\\''ar'"
-*)
-
 type call_result =
   < stdout:string;
     stderr:string;
@@ -44,12 +38,6 @@ val call_full :
     @param env environment to run the command in.
 *)
 
-(*$T
-  call_full ~stdin:(`Str "abc") "cat" |> stdout = "abc"
-  call_full "echo %s" (escape_str "a'b'c") |> stdout = "a'b'c\n"
-  call_full "echo %s" "a'b'c" |> stdout = "abc\n"
-*)
-
 val call :
   ?bufsize:int ->
   ?stdin:[`Gen of string gen | `Str of string] ->
@@ -66,12 +54,6 @@ val call_stdout :
   ('a, Buffer.t, unit, string) format4 ->
   'a
 
-(*$T
-  call_stdout ~stdin:(`Str "abc") "cat" = "abc"
-  call_stdout "echo %s" (escape_str "a'b'c") = "a'b'c\n"
-  call_stdout "echo %s" "a'b'c" = "abc\n"
-*)
-
 type line = string
 
 type async_call_result =