sdk-ui: add test checking the pinned event cache is kept for different room instances

crates/matrix-sdk-ui/tests/integration/timeline/pinned_event.rs

@@ -184,6 +184,69 @@ async fn test_max_events_to_load_is_honored() {
     test_helper.server.reset().await;
 }
 
+#[async_test]
+async fn test_cached_events_are_kept_for_different_room_instances() {
+    let mut test_helper = TestHelper::new().await;
+    let room_id = test_helper.room_id.clone();
+
+    // Join the room
+    let _ = test_helper.setup_initial_sync_response().await;
+    test_helper.server.reset().await;
+
+    // Load initial timeline items: a text message and a `m.room.pinned_events`
+    // with event $1 and $2 pinned
+    let _ = test_helper
+        .setup_sync_response(vec![("$1", "in the end", false)], Some(vec!["$1", "$2"]))
+        .await;
+
+    let room = test_helper.client.get_room(&room_id).unwrap();
+    let timeline = Timeline::builder(&room)
+        .with_focus(TimelineFocus::PinnedEvents { max_events_to_load: 2 })
+        .build()
+        .await
+        .unwrap();
+
+    assert!(
+        timeline.live_back_pagination_status().await.is_none(),
+        "there should be no live back-pagination status for a focused timeline"
+    );
+
+    let (items, mut timeline_stream) = timeline.subscribe().await;
+
+    assert!(!items.is_empty()); // We just loaded some events
+    assert_pending!(timeline_stream);
+
+    assert!(test_helper.client.pinned_event_cache().get(event_id!("$1")).await.is_some());
+
+    // Drop the existing room and timeline instances
+    test_helper.server.reset().await;
+    drop(timeline_stream);
+    drop(timeline);
+    drop(room);
+
+    // Set up a sync response with only the pinned event ids and no events, so if they exist later
+    // we know they come from the cache
+    let _ = test_helper
+        .setup_sync_response(Vec::new(), Some(vec!["$1", "$2"]))
+        .await;
+
+    // Get a new room instance
+    let room = test_helper.client.get_room(&room_id).unwrap();
+
+    // And a new timeline one
+    let timeline = Timeline::builder(&room)
+        .with_focus(TimelineFocus::PinnedEvents { max_events_to_load: 2 })
+        .build()
+        .await
+        .unwrap();
+
+    let (items, _) = timeline.subscribe().await;
+    assert!(!items.is_empty()); // These events came from the cache
+    assert!(test_helper.client.pinned_event_cache().get(event_id!("$1")).await.is_some());
+
+    test_helper.server.reset().await;
+}
+
 struct TestHelper {
     pub client: Client,
     pub server: MockServer,