watchlist add: event only if inserted; adr 0015 jetstream/relay accuracy; drop vacuous assert

crates/adapters/sqlite/tests/repositories/outbox_writes_test.rs

@@ -200,6 +200,24 @@ async fn adding_a_watchlist_entry_writes_the_entry_and_its_event_in_one_commit()
     assert_eq!(count(&pool, "event_queue").await, 1);
 }
 
+#[tokio::test]
+async fn re_adding_a_watchlist_entry_enqueues_no_second_event() {
+    let (pool, user_id, movie) = watchlist_fixture().await;
+    let repo = SqliteWatchlistRepository::new(pool.clone());
+    let first = WatchlistEntry::new(user_id.clone(), movie.id().clone());
+    repo.add(&first, &[watchlist_added(&first, &movie)])
+        .await
+        .unwrap();
+    let again = WatchlistEntry::new(user_id, movie.id().clone());
+
+    repo.add(&again, &[watchlist_added(&again, &movie)])
+        .await
+        .unwrap();
+
+    assert_eq!(count(&pool, "watchlist_entries").await, 1);
+    assert_eq!(count(&pool, "event_queue").await, 1, "no phantom event");
+}
+
 #[tokio::test]
 async fn a_failing_enqueue_rolls_back_the_watchlist_add() {
     let (pool, user_id, movie) = watchlist_fixture().await;