Integration: #2497 test subsequence playback in the Source monitor with and without sound

crates/ui-egui/tests/it/source_playback_ui.rs

@@ -230,3 +230,50 @@ fn j_and_l_shuttle_the_source_both_ways_and_double_the_speed() {
     assert!(!h.state().playback.playing);
     assert_eq!(h.state().session.project.to_json(), before);
 }
+
+/// A Source monitor session of the demo project's active sequence, with `Out` as the audio device.
+fn sequence_in_source(prepare: impl FnOnce(&mut Session)) -> (FilmcraftApp, Arc<Mutex<Option<Fill>>>) {
+    let mut session = Session::default();
+    session.execute("file.openDemoProject", json!({})).unwrap();
+    prepare(&mut session);
+    let seq = session.state.active_sequence.expect("a sequence").0;
+    session.execute("source.open", json!({"item": seq})).unwrap();
+    let fill = Arc::new(Mutex::new(None));
+    let mut app = FilmcraftApp::new(session);
+    app.audio = Some(Box::new(Out { frames: Arc::new(AtomicU64::new(0)), fill: fill.clone(), stalled: false }));
+    (app, fill)
+}
+
+#[test]
+fn a_sequence_with_sound_plays_in_the_source_monitor_through_the_device() {
+    let (app, fill) = sequence_in_source(|_| {});
+    let mut h = Harness::builder().with_step_dt(0.25).with_size(egui::vec2(1280.0, 800.0)).build_eframe(move |_cc| app);
+    h.step();
+    h.state_mut().play_source().unwrap();
+    for _ in 0..4 {
+        h.step();
+    }
+    assert!(h.state().source_playback.clock.playing);
+    assert!(h.state().source_playback.clock.audio_clock, "the sequence's sound drives the clock");
+    assert!(fill.lock().unwrap().is_some(), "the sequence's sound reaches the output");
+    h.state_mut().stop_source();
+}
+
+#[test]
+fn a_sequence_without_sound_plays_in_the_source_monitor_without_starting_the_output() {
+    let (app, fill) = sequence_in_source(|s| {
+        s.execute("file.newSequence", json!({"name": "Silent", "width": 1280, "height": 720, "fps": 24})).unwrap();
+        let picture = s.project.items.values().find(|i| i.as_media().is_some_and(|m| m.info.video.is_some())).expect("a picture item").id.0;
+        s.execute("timeline.place", json!({"item": picture, "track": "V1", "time": 0, "insert": false, "audio": false})).unwrap();
+    });
+    let mut h = Harness::builder().with_step_dt(0.25).with_size(egui::vec2(1280.0, 800.0)).build_eframe(move |_cc| app);
+    h.step();
+    h.state_mut().play_source().unwrap();
+    for _ in 0..4 {
+        h.step();
+    }
+    assert!(h.state().source_playback.clock.playing);
+    assert!(!h.state().source_playback.clock.audio_clock);
+    assert!(fill.lock().unwrap().is_none(), "no sound, so no output stream");
+    h.state_mut().stop_source();
+}