test(db): cover zero-label term and duplicate vocabulary key; use try_get in vocabulary_by_key

crates/db/tests/vocab.rs

@@ -73,6 +73,48 @@ async fn term_with_multilingual_labels_round_trips(pool: PgPool) {
     assert_eq!(listed[0].id, term_id);
 }
 
+#[sqlx::test]
+async fn term_with_no_labels_round_trips_empty(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    let v = vocab::create_vocabulary(db.pool(), "material")
+        .await
+        .unwrap();
+
+    let mut tx = db.pool().begin().await.unwrap();
+    let term_id = vocab::add_term(
+        &mut *tx,
+        &NewTerm {
+            vocabulary_id: v.id,
+            external_uri: None,
+            labels: vec![],
+        },
+    )
+    .await
+    .unwrap();
+    tx.commit().await.unwrap();
+
+    let term = vocab::term_by_id(db.pool(), term_id)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(term.labels.is_empty());
+}
+
+#[sqlx::test]
+async fn duplicate_vocabulary_key_is_rejected(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    vocab::create_vocabulary(db.pool(), "material")
+        .await
+        .unwrap();
+    let err = vocab::create_vocabulary(db.pool(), "material")
+        .await
+        .unwrap_err();
+    assert!(
+        matches!(err, sqlx::Error::Database(_)),
+        "expected a unique-violation DB error, got: {err:?}"
+    );
+}
+
 #[sqlx::test]
 async fn resolve_term_checks_vocabulary_membership(pool: PgPool) {
     let db = Db::from_pool(pool);