diff --git a/src/app/learnocaml_teacher_tab.ml b/src/app/learnocaml_teacher_tab.ml
index 9d3b1ad2e..b9bc2e5d5 100644
--- a/src/app/learnocaml_teacher_tab.ml
+++ b/src/app/learnocaml_teacher_tab.ml
@@ -1032,73 +1032,23 @@ let rec teacher_tab token _select _params () =
          current_assignment)
   in
   let set_assignment ?assg ?students ?exos ?default id =
+    (* - get the currently saved assignment *)
     let (assg0, students0, exos0, default0) = Hashtbl.find assignments_tbl id in
+    (* - update the assignment fields if related arg <> None *)
     let dft x0 = function Some x -> x | None -> x0 in
     let start, stop = dft assg0 assg in
     let students = dft students0 students in
     let exos = dft exos0 exos in
     let default = dft default0 default in
+    (* - update the assignment *)
     Hashtbl.replace assignments_tbl id
       ((start, stop), students, exos, default);
     (match Manip.by_id (assg_line_id id) with
      | Some l -> Manip.replaceSelf l (assignment_line id)
      | None -> failwith "Assignment line not found");
-    let status = ES.(Assigned {start; stop}) in
+    (* - update (!status_changes : ES.t SMap.t) (initially empty) *)
     let exercise_status_changes =
-      SSet.fold (fun ex_id acc ->
-          let st = get_status ex_id in
-          let assg = st.ES.assignments in
-          let old_default = assg.ES.default in
-          let new_default =
-            if default then status
-            else if default0 then ES.Closed
-            else old_default
-          in
-          let add tk st tmap =
-            if st = new_default then tmap
-            else Token.Map.add tk st tmap
-          in
-          let token_map =
-            Token.Map.fold (fun tk _ acc ->
-                if Token.Set.mem tk students then
-                  if default then acc
-                  else Token.Map.add tk status acc
-                else if Token.Set.mem tk students0 then
-                  if default then Token.Map.add tk ES.Closed acc
-                  else Token.Map.remove tk acc
-                else add tk (ES.get_status tk assg) acc)
-              !students_map Token.Map.empty
-          in
-          SMap.add ex_id
-            ES.{st with assignments = {
-                token_map;
-                default = new_default;
-              }}
-            acc)
-        exos
-        !status_changes
-    in
-    let exercise_status_changes =
-      SSet.fold (fun ex_id acc ->
-          let st = get_status ex_id in
-          let assg = st.ES.assignments in
-          let dft_status =
-            if default0 then ES.Closed else ES.default_assignment assg
-          in
-          let token_map =
-            Token.Set.fold Token.Map.remove students0 assg.ES.token_map
-          in
-          let token_map =
-            Token.Map.filter (fun _ a -> a <> dft_status) token_map
-          in
-          SMap.add ex_id
-            ES.{st with assignments = {
-                token_map;
-                default = dft_status
-              }}
-            acc)
-        (SSet.diff exos0 exos)
-        exercise_status_changes
+      ES.update_exercise_assignments get_status (students0, exos0, default0) (students, exos, default) (start, stop) !students_map !status_changes
     in
     status_changes := exercise_status_changes;
     fill_exercises_pane ();
diff --git a/src/state/learnocaml_data.ml b/src/state/learnocaml_data.ml
index 9b94d7fda..0b73156a7 100644
--- a/src/state/learnocaml_data.ml
+++ b/src/state/learnocaml_data.ml
@@ -626,7 +626,75 @@ module Exercise = struct
       | GloballyOpen -> a
       | GloballyInconsistent -> fix_open_close ~close:false a
 
-    (* Note/Erik: we may also want to implement set_assigned_globally *)
+    let update_exercise_assignments (get_status_t : string -> t) (students0, exos0, default0) (students, exos, default) (start, stop) students_map status_map =
+      let status = Assigned {start; stop} in
+      (* - walk accross the new list of exos *)
+      let status_map =
+        SSet.fold (fun ex_id acc ->
+            let st = get_status_t ex_id in
+            let assg = st.assignments in
+            let global_status = is_open_or_assigned_globally assg in
+            let old_default = assg.default in
+            let new_default =
+              if default then status
+              else if default0 (* the future_students flag was removed *)
+              then match global_status with
+                   | GloballyOpenOrAssigned | GloballyOpen -> Open
+                   | _ -> Closed
+              else old_default
+            in
+            let add tk st tmap =
+              if st = new_default then tmap (* normalize the token map *)
+              else Token.Map.add tk st tmap
+            in
+            let token_map =
+              Token.Map.fold (fun tk _ acc ->
+                  if Token.Set.mem tk students then
+                    if default then acc
+                    else Token.Map.add tk status acc
+                  else if Token.Set.mem tk students0 then (* the student was unassigned *)
+                    if default
+                    then match global_status with
+                         | GloballyOpenOrAssigned | GloballyOpen -> Token.Map.add tk Open acc
+                         | _ -> Token.Map.add tk Closed acc
+                    else (* Token.Map.remove tk (unneeded call) *) acc
+                  else add tk (get_status tk assg) acc)
+                students_map Token.Map.empty
+            in
+            SMap.add ex_id
+              {st with assignments = {
+                  token_map;
+                  default = new_default;
+              }}
+              acc)
+          exos
+          status_map
+      in
+      (* - walk accross the list of removed exos *)
+      SSet.fold (fun ex_id acc ->
+          let st = get_status_t ex_id in
+          let assg = st.assignments in
+          let dft_status =
+            if default0 (* the old default was Assigned(_, _) *)
+            then match is_open_or_assigned_globally assg with
+                 | GloballyOpenOrAssigned | GloballyOpen -> Open
+                 | _ -> Closed
+            else default_assignment assg
+          in
+          let token_map =
+            Token.Set.fold Token.Map.remove students0 assg.token_map
+          in
+          let token_map =
+            Token.Map.filter (fun _ a -> a <> dft_status) token_map
+          in
+          SMap.add ex_id
+            {st with assignments = {
+                token_map;
+                default = dft_status
+            }}
+            acc)
+        (SSet.diff exos0 exos)
+        status_map
 
     let is_open_assignment token a =
       match get_status token a with
diff --git a/src/state/learnocaml_data.mli b/src/state/learnocaml_data.mli
index b80bb7ec5..2af6ed0a3 100644
--- a/src/state/learnocaml_data.mli
+++ b/src/state/learnocaml_data.mli
@@ -251,6 +251,18 @@ module Exercise: sig
     (** Call [check_open_close] then (if need be) [fix_open_close] *)
     val check_and_fix_open_close: assignments -> assignments
 
+    (** Update [status_map: Exercise.Status.t SMap.t] if an assignment changes:
+        [update_exercise_assignments g (s0,e0,d0) (s,e,d) (t0,t1) m status_map]
+        turns [(stu0,exo0,dft0)] to [(s,e,d) + Assigned{t0;t1}] in [status_map]
+        from [g = get_status_t: string -> t] (status of exo) and [m = stud_map] *)
+    val update_exercise_assignments: (string -> t) ->
+      Token.Set.t * SSet.t * bool ->
+      Token.Set.t * SSet.t * bool ->
+      float * float ->
+      Student.t Token.Map.t ->
+      t SMap.t ->
+      t SMap.t
+
     val is_open_assignment:
       Token.t -> assignments -> [> `Open | `Closed | `Deadline of float]
 
diff --git a/src/state/learnocaml_data_test.ml b/src/state/learnocaml_data_test.ml
index ee4cf5d45..8bae7c0be 100644
--- a/src/state/learnocaml_data_test.ml
+++ b/src/state/learnocaml_data_test.ml
@@ -10,11 +10,12 @@
    See <https://dune.readthedocs.io/en/stable/tests.html#inline-tests> *)
 
 open Learnocaml_data
-open Exercise.Status
 
-let%test_module _ =
+let%test_module "Exercise.Status" =
   (module struct
 
+     open Exercise.Status
+
      let testdata_str_of_globalstatus = function
        | GloballyOpen -> "GloballyOpen"
        | GloballyClosed -> "GloballyClosed"
@@ -22,44 +23,71 @@ let%test_module _ =
        | GloballyClosedOrAssigned -> "GloballyClosedOrAssigned"
        | GloballyInconsistent -> "GloballyInconsistent"
 
-     let testdata_map_of list =
+
+     let testdata_smap_of list =
+       List.fold_right (fun (e, st) res -> SMap.add e st res) list SMap.empty
+
+     let testdata_list_of_smap map =
+       let list =
+         SMap.fold (fun e st res -> (e, st) :: res) map []
+       in
+       List.sort (fun (e1, _) (e2, _) -> compare e1 e2) list
+
+     let testdata_tokmap_of list =
        List.fold_right (fun (tok, st) res -> Token.Map.add tok st res) list Token.Map.empty
 
+     let testdata_list_of_tokmap map =
+       let list =
+         Token.Map.fold (fun tok st res -> (tok, st) :: res) map []
+       in
+       List.sort (fun (tok1, _) (tok2, _) -> compare tok1 tok2) list
+
+     let testdata_tokset_of list =
+       List.fold_right (fun (tok) res -> Token.Set.add tok res) list Token.Set.empty
+
+     let testdata_sset_of list =
+       List.fold_right (fun (tok) res -> SSet.add tok res) list SSet.empty
+
      let testdata_token : Token.t * Token.t  =
-       (Token.parse "KOK-W3L-NE1-SVY", Token.parse "JBG-B9B-3S1-NZO")
+       (Token.parse "JBG-B9B-3S1-NZO", Token.parse "KOK-W3L-NE1-SVY")
+
+     let testdata_assigned_7d = Assigned {start=1691877600.; stop=1692482400.}
 
-     let testdata_assigned = Assigned {start=1691877600.; stop=1692482400.}
+     let testdata_assigned_8d = Assigned {start=1691877600.; stop=1692568800.}
+
+     let testdata_7d = (1691877600., 1692482400.)
+
+     let testdata_8d = (1691877600., 1692568800.)
 
      let testdata_wrong_assignments =
        List.map (fun (mp, dflt) -> make_assignments mp dflt)
-         [(testdata_map_of [fst testdata_token, Open], Closed);
-          (testdata_map_of [fst testdata_token, Closed], Open);
-          (testdata_map_of [fst testdata_token, Open;
-                            snd testdata_token, Closed], testdata_assigned)]
+         [(testdata_tokmap_of [fst testdata_token, Open], Closed);
+          (testdata_tokmap_of [fst testdata_token, Closed], Open);
+          (testdata_tokmap_of [fst testdata_token, Open;
+                            snd testdata_token, Closed], testdata_assigned_7d)]
 
      let testdata_fixed_assignments =
        List.map (fun (mp, dflt) -> make_assignments mp dflt)
          (* Replace Open with Closed in testdata_wrong_assignments *)
-         [(testdata_map_of [fst testdata_token, Closed], Closed);
-          (testdata_map_of [fst testdata_token, Closed], Closed);
-          (testdata_map_of [fst testdata_token, Closed;
-                            snd testdata_token, Closed], testdata_assigned)]
+         [(testdata_tokmap_of [fst testdata_token, Closed], Closed);
+          (testdata_tokmap_of [fst testdata_token, Closed], Closed);
+          (testdata_tokmap_of [fst testdata_token, Closed;
+                            snd testdata_token, Closed], testdata_assigned_7d)]
 
      let testdata_good_assignments =
        List.map (fun (mp, dflt) -> make_assignments mp dflt)
-         [(*1*) (testdata_map_of [], Open);
-          (*2*) (testdata_map_of [], Closed);
-          (*3*) (testdata_map_of [], testdata_assigned);
-          (*4*) (testdata_map_of [fst testdata_token, Open], testdata_assigned);
-          (*5*) (testdata_map_of [fst testdata_token, Closed], testdata_assigned);
-          (*6*) (testdata_map_of [fst testdata_token, testdata_assigned], Open);
-          (*7*) (testdata_map_of [fst testdata_token, testdata_assigned], Closed);
-          (*8*) (testdata_map_of [fst testdata_token, Open], Open);
-          (*9*) (testdata_map_of [fst testdata_token, Closed], Closed);
-          (*10*)(testdata_map_of [fst testdata_token,
-                                  testdata_assigned], testdata_assigned)]
-
-     let%expect_test "is_open_or_assigned_globally" =
+         [(*1*) (testdata_tokmap_of [], Open);
+          (*2*) (testdata_tokmap_of [], Closed);
+          (*3*) (testdata_tokmap_of [], testdata_assigned_7d);
+          (*4*) (testdata_tokmap_of [fst testdata_token, Open], testdata_assigned_7d);
+          (*5*) (testdata_tokmap_of [fst testdata_token, Closed], testdata_assigned_7d);
+          (*6*) (testdata_tokmap_of [fst testdata_token, testdata_assigned_7d], Open);
+          (*7*) (testdata_tokmap_of [fst testdata_token, testdata_assigned_7d], Closed);
+          (*8*) (testdata_tokmap_of [fst testdata_token, Open], Open);
+          (*9*) (testdata_tokmap_of [fst testdata_token, Closed], Closed);
+          (*10*)(testdata_tokmap_of [fst testdata_token, testdata_assigned_7d], testdata_assigned_7d)]
+
+     let%expect_test "is_open_or_assigned_globally/full" =
        List.iter (fun glob -> Printf.printf "%s\n"
                               @@ testdata_str_of_globalstatus
                               @@ is_open_or_assigned_globally glob)
@@ -101,4 +129,414 @@ let%test_module _ =
        List.for_all (fun a -> check_and_fix_open_close a = a)
          testdata_good_assignments
 
+     let testdata_make_t id a dflt =
+       {id;
+        skills_prereq = []; (* independent of the SUT *)
+        skills_focus = []; (* independent of the SUT *)
+        assignments = make_assignments a dflt}
+
+     (* - initial status_map *)
+     let testdata_s0 : t SMap.t =
+       testdata_smap_of
+         [(* testdata_t0_a7d *)
+          ("exo1", testdata_make_t "exo1"
+                     (testdata_tokmap_of [snd testdata_token, Open]) testdata_assigned_7d);
+          ("exo2", testdata_make_t "exo2"
+                     (testdata_tokmap_of [snd testdata_token, Closed]) testdata_assigned_7d);
+          ("exo3", testdata_make_t "exo3"
+                     (testdata_tokmap_of []) testdata_assigned_7d);
+          (* testdata_t0_a8d *)
+          ("exo4", testdata_make_t "exo4"
+                     (testdata_tokmap_of [fst testdata_token, testdata_assigned_8d]) Open);
+          ("exo5", testdata_make_t "exo5"
+                     (testdata_tokmap_of [fst testdata_token, testdata_assigned_8d]) Closed);
+          (* testdata_t0_noa *)
+          ("exo6", testdata_make_t "exo6"
+                     (testdata_tokmap_of []) Open);
+          ("exo7", testdata_make_t "exo7"
+                     (testdata_tokmap_of []) Closed);
+         ]
+
+     (* let testdata_s00 : t SMap.t = SMap.empty *)
+
+     type triple = Token.Set.t * SSet.t * bool
+
+     let testdata_t0_a7d : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo1"; "exo2"; "exo3"],
+        true)
+
+     let testdata_t0_a8d : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo4"; "exo5"],
+        false)
+
+     (* let testdata_t0_noa : triple =
+       (testdata_tokset_of [],
+        testdata_sset_of [],
+        false) *)
+
+     let%expect_test "is_open_or_assigned_globally/testdata_s0" =
+       List.iter (fun glob -> Printf.printf "%s\n"
+                              @@ testdata_str_of_globalstatus
+                              @@ is_open_or_assigned_globally glob)
+         (List.map (fun (_e, s) -> s.assignments) @@ testdata_list_of_smap testdata_s0);
+       [%expect {|
+         GloballyOpenOrAssigned
+         GloballyClosedOrAssigned
+         GloballyClosedOrAssigned
+         GloballyOpenOrAssigned
+         GloballyClosedOrAssigned
+         GloballyOpen
+         GloballyClosed |}]
+
+     let testdata_str_of_status = function
+       | Open -> "Open"
+       | Closed -> "Closed"
+       | Assigned {start; stop} -> Printf.sprintf "Assigned(%s,%s)"
+                                    (string_of_float start)
+                                    (string_of_float stop)
+
+     let testdata_str_of_toklist list =
+       List.fold_right (fun (tok, st) r ->
+           Printf.sprintf "(%s, %s); %s"
+             (Token.to_string tok)
+             (testdata_str_of_status st)
+             r) list ""
+
+     let testdata_str_of_assignments (s : assignments) =
+       Printf.sprintf "{default = %s; token_map = { %s}}"
+         (testdata_str_of_status s.default)
+         (testdata_str_of_toklist @@
+            testdata_list_of_tokmap s.token_map)
+
+     let testdata_str_of_t (s : t) =
+       Printf.sprintf "{id = %s; assignments = %s}"
+         s.id
+         (testdata_str_of_assignments s.assignments)
+
+     let testdata_str_of_smap ?(globalstatus=true) (s : t SMap.t) =
+       let list =
+         SMap.fold (fun eid tt acc ->
+             if eid <> tt.id
+             then failwith (Printf.sprintf "eid(%s) <> tt.id(%s)" eid tt.id)
+             else (eid, testdata_str_of_t tt ^
+                          (if globalstatus
+                           then " -> " ^
+                                  testdata_str_of_globalstatus
+                                  @@ is_open_or_assigned_globally
+                                  @@ tt.assignments
+                           else "")) :: acc) s []
+       in
+       let list =
+         List.sort (fun (eid1, _) (eid2, _) -> compare eid1 eid2) list
+       in
+       List.fold_right (fun (_, st) r -> st ^ "\n" ^ r) list ""
+
+     let testdata_get_status_t status_map id =
+       try SMap.find id status_map with Not_found ->
+         default id
+
+     let testdata_stud_map =
+       let stud_of_tok tk = (tk, Student.default tk) in
+       testdata_tokmap_of [stud_of_tok @@ fst testdata_token;
+                           stud_of_tok @@ snd testdata_token]
+
+     (* Test cases candidates :
+        Usage of function set_assignment in learnocaml_teacher_tab.ml
+        - set_assignment aid ~exos (*selected exos*)
+        - set_assignment aid ~students ~default (*selected students*)
+        - set_assignment aid ~assg:(start,stop) (*change assignment*)
+        - set_assignment aid ~students:() ~exos:() (*assignment_remove*)
+      *)
+
+     let testdata_t1_a7d_rm_exo1 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo2"; "exo3"],(*<-*)
+        true)
+     let testdata_t1_a7d_rm_exo2 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo1"; "exo3"],(*<-*)
+        true)
+     let testdata_t1_a7d_rm_exo3 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo1"; "exo2"],(*<-*)
+        true)
+     let testdata_t1_a7d_add_exo6_7 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo1"; "exo2"; "exo3"; "exo6"; "exo7"],(*<-*)
+        true)
+
+     let testdata_t1_a8d_rm_exo4 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo5"],(*<-*)
+        false)
+     let testdata_t1_a8d_rm_exo5 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo4"],(*<-*)
+        false)
+     let testdata_t1_a8d_add_exo6_7 : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo4"; "exo5"; "exo6"; "exo7"],(*<-*)
+        false)
+
+     let%expect_test "update_exercise_assignments/set_exos" =
+       Printf.printf "# initial status_map:\n%s\n" @@
+         testdata_str_of_smap testdata_s0;
+       List.iter (fun (label, tri0, tri, dates) ->
+           Printf.printf "# %s:\n%s\n"
+             label (testdata_str_of_smap @@
+                      update_exercise_assignments (testdata_get_status_t testdata_s0)
+                        tri0 tri dates testdata_stud_map testdata_s0))
+         ["a7d_rm_exo1", testdata_t0_a7d, testdata_t1_a7d_rm_exo1, testdata_7d;
+          "a7d_rm_exo2", testdata_t0_a7d, testdata_t1_a7d_rm_exo2, testdata_7d;
+          "a7d_rm_exo3", testdata_t0_a7d, testdata_t1_a7d_rm_exo3, testdata_7d;
+          "a7d_add_exo6_7_true", testdata_t0_a7d, testdata_t1_a7d_add_exo6_7, testdata_7d;
+          "a8d_rm_exo4", testdata_t0_a8d, testdata_t1_a8d_rm_exo4, testdata_8d;
+          "a8d_rm_exo5", testdata_t0_a8d, testdata_t1_a8d_rm_exo5, testdata_8d;
+          "a8d_add_exo6_7_false", testdata_t0_a8d, testdata_t1_a8d_add_exo6_7, testdata_8d;
+         ];
+       [%expect {|
+         # initial status_map:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_rm_exo1:
+         {id = exo1; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_rm_exo2:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_rm_exo3:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_add_exo6_7_true:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo7; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+
+         # a8d_rm_exo4:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a8d_rm_exo5:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a8d_add_exo6_7_false:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo7; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned |}]
+
+     let testdata_t2_a7d_add_stu2 : triple =
+       (testdata_tokset_of [fst testdata_token; snd testdata_token],(*<-*)
+        testdata_sset_of ["exo1"; "exo2"; "exo3"],
+        true)
+
+     let testdata_t2_a7d_rm_stu1 : triple =
+       (testdata_tokset_of [],(*<-*)
+        testdata_sset_of ["exo1"; "exo2"; "exo3"],
+        true)
+
+     let testdata_t2_a7d_rm_dflt : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo1"; "exo2"; "exo3"],
+        false(*<-*))
+
+     let testdata_t2_a8d_add_stu2 : triple =
+       (testdata_tokset_of [fst testdata_token; snd testdata_token],(*<-*)
+        testdata_sset_of ["exo4"; "exo5"],
+        false)
+
+     let testdata_t2_a8d_add_dflt : triple =
+       (testdata_tokset_of [fst testdata_token],
+        testdata_sset_of ["exo4"; "exo5"],
+        true(*<-*))
+
+     let%expect_test "update_exercise_assignments/set_students" =
+       Printf.printf "# initial status_map:\n%s\n" @@
+         testdata_str_of_smap testdata_s0;
+       List.iter (fun (label, tri0, tri, dates) ->
+           Printf.printf "# %s:\n%s\n"
+             label (testdata_str_of_smap @@
+                      update_exercise_assignments (testdata_get_status_t testdata_s0)
+                        tri0 tri dates testdata_stud_map testdata_s0))
+         ["a7d_add_stu2", testdata_t0_a7d, testdata_t2_a7d_add_stu2, testdata_7d;
+          "a7d_rm_stu1", testdata_t0_a7d, testdata_t2_a7d_rm_stu1, testdata_7d;
+          "a7d_rm_dflt", testdata_t0_a7d, testdata_t2_a7d_rm_dflt, testdata_7d;
+          "a8d_add_stu2", testdata_t0_a8d, testdata_t2_a8d_add_stu2, testdata_8d;
+          "a8d_add_dflt", testdata_t0_a8d, testdata_t2_a8d_add_dflt, testdata_8d;
+         ];
+       [%expect {|
+         # initial status_map:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_add_stu2:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_rm_stu1:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (JBG-B9B-3S1-NZO, Open); (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (JBG-B9B-3S1-NZO, Closed); (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (JBG-B9B-3S1-NZO, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_rm_dflt:
+         {id = exo1; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692482400.)); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692482400.)); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692482400.)); (KOK-W3L-NE1-SVY, Assigned(1691877600.,1692482400.)); }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a8d_add_stu2:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); (KOK-W3L-NE1-SVY, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); (KOK-W3L-NE1-SVY, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a8d_add_dflt:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Assigned(1691877600.,1692568800.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Assigned(1691877600.,1692568800.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed |}]
+
+     let testdata_t3_a7d_rm_assignment : triple =
+       (testdata_tokset_of [],(*<-*)
+        testdata_sset_of [],(*<-*)
+        true)
+
+     let testdata_t3_a8d_rm_assignment : triple =
+       (testdata_tokset_of [],(*<-*)
+        testdata_sset_of [],(*<-*)
+        false)
+
+     let%expect_test "update_exercise_assignments/rm_assignment" =
+       Printf.printf "# initial status_map:\n%s\n" @@
+         testdata_str_of_smap testdata_s0;
+       List.iter (fun (label, tri0, tri, dates) ->
+           Printf.printf "# %s:\n%s\n"
+             label (testdata_str_of_smap @@
+                      update_exercise_assignments (testdata_get_status_t testdata_s0)
+                        tri0 tri dates testdata_stud_map testdata_s0))
+         ["a7d_rm_assignment", testdata_t0_a7d, testdata_t3_a7d_rm_assignment, testdata_7d;
+          "a8d_rm_assignment", testdata_t0_a8d, testdata_t3_a8d_rm_assignment, testdata_8d];
+       [%expect {|
+         # initial status_map:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_rm_assignment:
+         {id = exo1; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo2; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+         {id = exo3; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a8d_rm_assignment:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo5; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed |}]
+
+     let%expect_test "update_exercise_assignments/set_assignment" =
+       Printf.printf "# initial status_map:\n%s\n" @@
+         testdata_str_of_smap testdata_s0;
+       List.iter (fun (label, tri0, tri, dates) ->
+           Printf.printf "# %s:\n%s\n"
+             label (testdata_str_of_smap @@ (* let _ = *)
+                      update_exercise_assignments (testdata_get_status_t testdata_s0)
+                      tri0 tri dates testdata_stud_map testdata_s0 (* in testdata_s0 *)))
+         ["a7d_to_a8d", testdata_t0_a7d, testdata_t0_a7d, testdata_8d];
+       [%expect {|
+         # initial status_map:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692482400.); token_map = { }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed
+
+         # a7d_to_a8d:
+         {id = exo1; assignments = {default = Assigned(1691877600.,1692568800.); token_map = { (KOK-W3L-NE1-SVY, Open); }}} -> GloballyOpenOrAssigned
+         {id = exo2; assignments = {default = Assigned(1691877600.,1692568800.); token_map = { (KOK-W3L-NE1-SVY, Closed); }}} -> GloballyClosedOrAssigned
+         {id = exo3; assignments = {default = Assigned(1691877600.,1692568800.); token_map = { (KOK-W3L-NE1-SVY, Assigned(1691877600.,1692482400.)); }}} -> GloballyClosedOrAssigned
+         {id = exo4; assignments = {default = Open; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyOpenOrAssigned
+         {id = exo5; assignments = {default = Closed; token_map = { (JBG-B9B-3S1-NZO, Assigned(1691877600.,1692568800.)); }}} -> GloballyClosedOrAssigned
+         {id = exo6; assignments = {default = Open; token_map = { }}} -> GloballyOpen
+         {id = exo7; assignments = {default = Closed; token_map = { }}} -> GloballyClosed |}]
+
    end)