test(of): pin the Mary Mother of the Church / Anthony of Padua tie

data/of/amendments/006-mary-mother-of-the-church.sexp's own header
documented, at length, that Easter+50 can land on 13 June and tie with
Anthony of Padua at Tabula III.10 (both universal Memoria_obligatoria)
-- the ledger's remedy (F-MEMORIAL-TIE) asked to document the lacuna
AND pin the current behaviour so it cannot drift silently. Only the
documentation half was done.

Add test_mater_ecclesiae_anthony_tie_2011_known_arbitrary, in the same
style as the Joseph/Palm Sunday and Holy Family fallback pins already
in this file, but labelled KNOWN ARBITRARY rather than KNOWN WRONG:
no rubric decides this collision (the 2018 decree is silent on it, and
Normae n. 14's third clause resolves only the ad-libitum/ad-libitum
case), so colitur's Slug.compare tie-break is a generic kernel
fallback, not a colitur-invented rule. Asserts the 2011 Easter/offset
arithmetic by hand, the current observed slug, and that the loser is
recorded in `omitted` rather than silently dropped.

1 files changed, 59 insertions, 1 deletions

diff --git a/test/test_rite_of.ml b/test/test_rite_of.ml
index d16bcf3..a1892ae 100644
--- a/test/test_rite_of.ml
+++ b/test/test_rite_of.ml
@@ -334,6 +334,60 @@ let test_holy_family_fallback_1583_known_wrong_ferial () =
   Alcotest.(check bool) "and that really is NOT the Holy Family (confirming this really is the defect)" false
     (slug_of dec30.LD.observed = "of-holy-family")
 
+(* Fix wave I6 (final-review.md, 2026-08-25-colitur-of-phases-3-5): the
+   obligatory-memorial tie data/of/amendments/006-mary-mother-of-the-church
+   .sexp's own header documents at length (its "*** FINDING ***" comment)
+   was documented but never PINNED -- the ledger's own remedy (F-MEMORIAL-TIE)
+   asked for both halves. Mary, Mother of the Church (Easter+50) and Anthony
+   of Padua (13 June, fixed) both band at Tabula III.10 (100, both universal
+   Memoria_obligatoria) in any year Easter+50 lands on 13 June; 2011 is the
+   worked example that amendment header itself names (Easter 24 April 2011,
+   so Easter+50 = 13 June -- re-derived here, not trusted from the comment).
+
+   KNOWN ARBITRARY, not KNOWN WRONG: unlike the two tests above, there is no
+   rubric this contradicts. The 2018 decree (AAS 110, 437-438) is silent on
+   a universal-calendar coincidence with an existing obligatory memorial, and
+   Normae n. 14's own third clause resolves only the AD-LIBITUM/AD-LIBITUM
+   case ("Si eodem die plures inscribuntur in calendario memoriae ad
+   libitum") -- it does not reach two OBLIGATORY memorials. So colitur's
+   Slug.compare tie-break ("anthony-of-padua-priest-and-doctor" sorts before
+   "mary-mother-of-the-church") is not this project inventing a rule; it is
+   the kernel's own generic, rite-agnostic fallback, applied here for lack of
+   a rite-specific one. This test pins that CURRENT behaviour so a future
+   Calendar/kernel change, a slug rename, or a future overlay cannot flip
+   which of the two is observed with no test going red -- the same shape of
+   invisible-drift risk the EF side's RG 113/[band] fidelity work (`ef-rg16a`,
+   register §6.1) eliminated on that side. *)
+let test_mater_ecclesiae_anthony_tie_2011_known_arbitrary () =
+  let easter_2011 = Computus.gregorian_easter 2011 in
+  Alcotest.(check string) "2011 Easter is really 24 April (the Easter+50 trigger)" "2011-04-24"
+    (Date.to_iso8601 easter_2011);
+  let tie_date = Date.add_days easter_2011 50 in
+  Alcotest.(check string) "Easter+50 2011 is really 13 June, coinciding with Anthony of Padua's fixed date"
+    "2011-06-13" (Date.to_iso8601 tie_date);
+  (* [Cal.year]'s own [y] labels an Advent-to-Advent LITURGICAL year, not a
+     civil one (year_bounds = [year_start y, year_start (y+1) - 1], and
+     [year_start] is Advent Sunday WITHIN civil year y) -- so 13 June 2011
+     falls inside liturgical year 2010 (Advent 2010 .. the eve of Advent
+     2011), the same off-by-one every other test in this file that reaches
+     for a spring date already accounts for (the Joseph test above uses
+     2061 to reach March 2062). *)
+  let days = Cal.year real_of_rite real_of_layer 2010 in
+  let june13 = Array.to_list days |> List.find (fun d -> Date.compare d.LD.date tie_date = 0) in
+  Alcotest.(check string)
+    "KNOWN ARBITRARY (no rubric decides this; see this test's own header): the kernel's generic \
+     alphabetical tie-break observes Anthony of Padua, not Mary Mother of the Church"
+    "anthony-of-padua-priest-and-doctor" (slug_of june13.LD.observed);
+  let mater_ecclesiae_omitted =
+    List.exists (fun (c, _) -> slug_of c = "mary-mother-of-the-church") june13.LD.omitted
+  in
+  Alcotest.(check bool)
+    "and Mary, Mother of the Church is recorded in `omitted`, not silently dropped -- {!Colitur_kernel \
+     .Liturgical_day.t.omitted}'s own contract"
+    true mater_ecclesiae_omitted;
+  Alcotest.(check bool) "she carries no commemoration either (OF's own admit always returns [])" false
+    (List.exists (fun (c, _) -> slug_of c = "mary-mother-of-the-church") june13.LD.commemorations)
+
 let suite =
   ( "Rite_of (real data: assembled Rite.t end-to-end via Calendar/Validate)",
     [ Alcotest.test_case "landmark years validate cleanly (modulo two documented gaps)" `Quick
@@ -349,4 +403,8 @@ let suite =
       Alcotest.test_case
         "NEWLY-FOUND DEFECT pinned, not fixed: Holy Family's Normae n.35(a) 30-December fallback is \
          unreached when Christmas Day is a Sunday (1583)" `Quick
-        test_holy_family_fallback_1583_known_wrong_ferial ] )
+        test_holy_family_fallback_1583_known_wrong_ferial;
+      Alcotest.test_case
+        "KNOWN ARBITRARY pinned: Mary Mother of the Church vs Anthony of Padua tie, 2011-06-13 \
+         (Easter+50)" `Quick
+        test_mater_ecclesiae_anthony_tie_2011_known_arbitrary ] )