test(precedence): strengthen accounting test, cover order and empty sanctoral

The accounting test only checked bucket lengths, which a mutant satisfies by
duplicating a candidate across two buckets while dropping another entirely.
Replace it with a sorted slug-set comparison (Alcotest.slist), which a
duplicate-or-missing slug both fail.

Add two cases the brief's three properties call for but nothing exercised:
input-order independence (permuting the sanctoral list must not change the
outcome) and a temporal-only day (empty sanctoral list), the case the
temporal/sanctoral split exists to make safe.

1 files changed, 39 insertions, 7 deletions

diff --git a/test/test_precedence.ml b/test/test_precedence.ml
index 39be06c..369c490 100644
--- a/test/test_precedence.ml
+++ b/test/test_precedence.ml
@@ -56,15 +56,45 @@ let test_commemoration_only_never_observed () =
   Alcotest.(check (list string)) "suppressed commemorated" [ "suppressed" ]
     (List.map (fun (c, _) -> slug_of c) r.P.commemorations)
 
-(* Anything the admit limit drops is recorded in `omitted`, never dropped silently. *)
+(* Anything the admit limit drops is recorded in `omitted`, never dropped silently
+   -- and each input candidate lands in exactly one bucket, not zero or two. *)
 let test_nothing_silently_lost () =
   let r = P.resolve rules ctx ~temporal:(cand ~origin:P.Temporal ~rank:Hi "sunday")
             ~sanctoral:[ cand ~rank:Lo "a"; cand ~rank:Lo "b"; cand ~rank:Lo "c" ] in
-  Alcotest.(check int) "two admitted" 2 (List.length r.P.commemorations);
-  Alcotest.(check int) "one recorded as omitted" 1 (List.length r.P.omitted);
-  let total = 1 + List.length r.P.commemorations + List.length r.P.deferred
-              + List.length r.P.omitted in
-  Alcotest.(check int) "every candidate accounted for" 4 total
+  let bucketed =
+    (slug_of r.P.observed
+     :: List.map (fun (c, _) -> slug_of c) r.P.commemorations)
+    @ List.map slug_of r.P.deferred
+    @ List.map (fun (c, _) -> slug_of c) r.P.omitted
+  in
+  Alcotest.(check (slist string compare)) "every candidate appears exactly once"
+    [ "a"; "b"; "c"; "sunday" ] bucketed;
+  Alcotest.(check int) "two admitted" 2 (List.length r.P.commemorations)
+
+(* The result must not depend on the order sanctoral candidates arrive in;
+   ties break on slug, not on list position. *)
+let test_order_independent () =
+  let a = cand ~rank:Lo "a" and b = cand ~rank:Lo "b" and c = cand ~rank:Lo "c" in
+  let t = cand ~origin:P.Temporal ~rank:Hi "sunday" in
+  let observed_for sanctoral = slug_of (P.resolve rules ctx ~temporal:t ~sanctoral).P.observed in
+  let comms_for sanctoral =
+    List.map (fun (x, _) -> slug_of x) (P.resolve rules ctx ~temporal:t ~sanctoral).P.commemorations
+  in
+  List.iter
+    (fun perm ->
+      Alcotest.(check string) "same observed" (observed_for [ a; b; c ]) (observed_for perm);
+      Alcotest.(check (list string)) "same commemorations" (comms_for [ a; b; c ]) (comms_for perm))
+    [ [ c; b; a ]; [ b; a; c ]; [ c; a; b ] ]
+
+(* The case the "pass temporal separately" design exists to make safe: a day
+   with no sanctoral candidate at all. *)
+let test_temporal_only_day () =
+  let r = P.resolve rules ctx ~temporal:(cand ~origin:P.Temporal ~rank:Lo "feria")
+            ~sanctoral:[] in
+  Alcotest.(check string) "feria observed" "feria" (slug_of r.P.observed);
+  Alcotest.(check int) "no commemorations" 0 (List.length r.P.commemorations);
+  Alcotest.(check int) "nothing deferred" 0 (List.length r.P.deferred);
+  Alcotest.(check int) "nothing omitted" 0 (List.length r.P.omitted)
 
 let suite =
   ( "Precedence",
@@ -73,4 +103,6 @@ let suite =
       Alcotest.test_case "loser dispositions" `Quick test_loser_dispositions;
       Alcotest.test_case "commemoration-only never observed" `Quick
         test_commemoration_only_never_observed;
-      Alcotest.test_case "nothing silently lost" `Quick test_nothing_silently_lost ] )
+      Alcotest.test_case "nothing silently lost" `Quick test_nothing_silently_lost;
+      Alcotest.test_case "order independent" `Quick test_order_independent;
+      Alcotest.test_case "temporal-only day" `Quick test_temporal_only_day ] )