test(validation): cover @vocab suppressing the coverage finding

docs/maintaining-meta-schemas.md

@@ -158,7 +158,9 @@ but nothing notices a check judging the literal context rather than the resolved
 
 ### Broken fixtures
 
-Each one exists to prove a specific check fires, rather than only that valid input passes.
+Each one exists to prove a specific check fires, rather than only that valid input passes. One is a
+control instead: the same schema without the defect, proving the check stays silent where the
+specification says it must.
 `tests/test_validation/test_pipeline.py` maps each file to the check it must trip.
 
 | Fixture | Trips |
@@ -179,6 +181,7 @@ Each one exists to prove a specific check fires, rather than only that valid inp
 | `root_ref_not_reflected` | `rule.context-reflects-refs` - a single `allOf` `$ref` is not reflected anywhere in `@context` |
 | `branch_context_conflict` | `rule.branch-context-conflict` - two `oneOf`-branch contexts map the same keyword to different IRIs at the root |
 | `narrow_only_relaxation` | `rule.narrow-only` - an `allOf` ancestor's `maximum` is relaxed rather than tightened (`NarrowBase.schema.json` is its sibling ancestor) |
+| `vocab_covers_the_remainder` | nothing, deliberately - `missing_context_term` with `@vocab` added and nothing else changed, the control for `context.coverage` |
 
 ## Why `id_base` is recorded and not assumed
 

src/oold/validation/check_registry.py

@@ -966,12 +966,13 @@ class CheckInfo:
         detects=check_predicates,
         predates_catalog=True,
     ),
-    # Deliberately cites no rule. The specification permits an unmapped term - "an author MAY
-    # leave it unmapped" - and treats deferring semantics as what distinguishes OO-LD from
-    # RDF/SHACL, so an unmapped property is not a conformance failure. It is still worth
-    # reporting: OOLD-SCH-21d7 says a schema should offer at least one complete mapping, which is
-    # a SHOULD, so the warning is the catalogue's own severity rather than one chosen here.
-    # Promote it with --strict where full coverage is intended.
+    # Cites OOLD-SCH-21d7, not the prefix rule the combined check used to borrow. The
+    # specification permits an unmapped term - "an author MAY leave it unmapped" - and treats
+    # deferring semantics as what distinguishes OO-LD from RDF/SHACL, so an unmapped property
+    # is not a conformance failure. It is still worth reporting: OOLD-SCH-21d7 says a schema
+    # should offer at least one complete mapping, which is a SHOULD, so the warning is the
+    # catalogue's own severity rather than one chosen here. Promote it with --strict where
+    # full coverage is intended.
     CheckInfo(
         "context.coverage",
         "every declared property carries a @context term",

tests/data/oold/broken/vocab_covers_the_remainder.schema.json

@@ -0,0 +1,19 @@
+{
+  "$schema": "https://oo-ld.org/latest/meta/oold-meta-schema.json",
+  "$id": "vocab_covers_the_remainder.schema.json",
+  "title": "VocabCoversTheRemainder",
+  "@context": {
+    "@vocab": "https://example.org/vocab/",
+    "ex": "https://example.org/",
+    "name": "ex:name"
+  },
+  "type": "object",
+  "properties": {
+    "name": {
+      "type": "string"
+    },
+    "orphan": {
+      "type": "string"
+    }
+  }
+}

tests/test_validation/test_pipeline.py

@@ -148,7 +148,8 @@ def test_missing_context_term_warns_and_names_the_orphan_property(broken_dir):
 
     `OOLD-SCH-2d05`: an implementation must not treat an unmapped term as a conformance failure.
     The prefix half of the old combined check keeps failing under `context.predicates`, which
-    does have a rule behind it; this half moved to `context.coverage`, which cites none.
+    does have a rule behind it; this half moved to `context.coverage`, which cites
+    `OOLD-SCH-21d7`, a SHOULD, which is why it warns.
     """
     report = validate_schema(broken_dir / "missing_context_term.schema.json", OFFLINE)
     checks = {c.id: c for c in report.checks}
@@ -182,6 +183,28 @@ def test_a_schema_with_no_context_warns_instead_of_failing_the_round_trip(broken
     assert not report.failures()
 
 
+def test_vocab_suppresses_the_coverage_finding(broken_dir):
+    """Declaring `@vocab` maps the remainder, so there is no unmapped term left to report.
+
+    The specification names `@vocab` as the way to stop unmapped terms being dropped silently,
+    so a schema that declares one has no coverage finding to make. This held before the split
+    of `context.predicates` into two checks and was verified only by an ad-hoc probe at the
+    time. The fixture is `missing_context_term.schema.json` with `@vocab` added and nothing
+    else changed, so a regression here is the split losing the permitted case rather than a
+    difference between the two schemas.
+    """
+    report = validate_schema(broken_dir / "vocab_covers_the_remainder.schema.json", OFFLINE)
+    checks = {c.id: c for c in report.checks}
+
+    coverage = checks["context.coverage"]
+    assert coverage.status == OK, coverage.message
+    # OK rather than SKIP: the check ran and found nothing, rather than standing down.
+    assert "context.coverage" not in {c.id for c in report.failures()}
+    # `orphan` carries no term of its own; @vocab is what maps it.
+    assert checks["context.predicates"].status == OK
+    assert checks["context.predicates"].detail["mapped"] == 2
+
+
 def test_a_processor_failure_is_not_downgraded_to_a_coverage_warning(broken_dir, monkeypatch):
     """A raised processor must not read as a permitted omission.