1 files changed, 30 insertions, 1 deletions
diff --git a/test/test_rite_ef.ml b/test/test_rite_ef.ml
index 4da6d73..f4991f3 100644
--- a/test/test_rite_ef.ml
+++ b/test/test_rite_ef.ml
@@ -526,9 +526,38 @@ let test_maurice_thomas_band_fidelity_end_to_end () =
     [ "maurice-and-companions-martyrs" ]
     (List.map (fun (c, _) -> slug_of c) day.LD.omitted)
 
+
+(* The SHIPPED example overlay (data/ef/examples/diocesan-example.sexp) is
+   documentation a user is invited to run and copy, and the man page names its
+   installed path. An example that silently stopped loading -- a directive
+   renamed, a Date_spec variant changed -- would be worse than shipping none,
+   because it would fail only for whoever tried it.
+
+   This asserts it PARSES against the REAL EF rank vocabulary and that it
+   still demonstrates the range it claims to. It deliberately does NOT assert
+   which days it produces: those celebrations are invented, and pinning their
+   dates would make an illustrative file behave like calendar data. *)
+let test_shipped_example_overlay_loads () =
+  let path = "../data/ef/examples/diocesan-example.sexp" in
+  match Overlay.load Rite_ef.Vocab_ef.rank_of_sexp path with
+  | Error e -> Alcotest.failf "the shipped example overlay must load: %s" e
+  | Ok o ->
+      Alcotest.(check string) "its id" "diocesan-example" o.Overlay.id;
+      Alcotest.(check bool) "it demonstrates at least four directives" true
+        (List.length o.Overlay.directives >= 4);
+      (* Applying it must be clean: a directive naming a slug the universal
+         calendar lacks would warn, and an EXAMPLE that warns teaches the
+         wrong lesson. *)
+      let layer = real_layer () in
+      let _, diagnostics = Overlay.apply layer o in
+      Alcotest.(check (list string)) "it applies with no diagnostics" []
+        (List.map Overlay.diagnostic_to_string diagnostics)
+
 let suite =
   ( "Rite_ef (real data: overlay-in-effect, domain-ceiling)",
-    [ Alcotest.test_case "the overlay suppression is observably in effect" `Quick
+    [ Alcotest.test_case "the shipped example overlay loads and applies cleanly" `Quick
+        test_shipped_example_overlay_loads;
+      Alcotest.test_case "the overlay suppression is observably in effect" `Quick
         test_vigil_of_christmas_suppressed;
       Alcotest.test_case "RG16(a) task: the two subject retags are in effect, the other four untouched"
         `Quick test_rg16a_subject_retag_in_effect;