jellyfin-qbittorrent-monitor: fix hysterisis

tests/jellyfin-qbittorrent-monitor.nix

@@ -586,6 +586,97 @@ pkgs.testers.runNixOSTest {
     time.sleep(2)
 
 
+    # === FLICKER TEST ===
+    #
+    # Session flicker (brief appear→disappear→reappear cycles) is the
+    # production reality when xmrig starves the transcode CPU and the
+    # client's buffer oscillates. The hysteresis timer must measure
+    # CONTIGUOUS absence, not cumulative gaps across flickers. A 5s
+    # stop delay with flickers of 2s absent / 2s present must NOT
+    # accumulate into a spurious unlimited transition.
+
+    server.succeed("systemctl stop monitor-test || true")
+    time.sleep(1)
+    server.succeed(f"""
+      systemd-run --unit=monitor-flicker \
+        --setenv=JELLYFIN_URL=http://localhost:8096 \
+        --setenv=JELLYFIN_API_KEY={token} \
+        --setenv=QBITTORRENT_URL=http://localhost:8080 \
+        --setenv=CHECK_INTERVAL=1 \
+        --setenv=STREAMING_START_DELAY=1 \
+        --setenv=STREAMING_STOP_DELAY=5 \
+        --setenv=TOTAL_BANDWIDTH_BUDGET=50000000 \
+        --setenv=SERVICE_BUFFER=2000000 \
+        --setenv=DEFAULT_STREAM_BITRATE=10000000 \
+        --setenv=MIN_TORRENT_SPEED=100 \
+        {python} {monitor}
+    """)
+    time.sleep(2)
+    assert not is_throttled(), "Should start unthrottled"
+
+    with subtest("Session flicker does not accumulate hysteresis timer"):
+        # Start playback
+        playback_flicker = {
+            "ItemId": movie_id,
+            "MediaSourceId": media_source_id,
+            "PlaySessionId": "test-play-session-flicker",
+            "CanSeek": True,
+            "IsPaused": False,
+        }
+        start_cmd = f"curl -sf -X POST 'http://{server_ip}:8096/Sessions/Playing' -d '{json.dumps(playback_flicker)}' -H 'Content-Type:application/json' -H 'X-Emby-Authorization:{client_auth}, Token={client_token}'"
+        client.succeed(start_cmd)
+        time.sleep(2)
+        assert is_throttled(), "Should throttle when streaming starts"
+
+        # Flicker 1: stop 2s, restart 2s
+        playback_flicker["PositionTicks"] = 50000000
+        stop_flicker = f"curl -sf -X POST 'http://{server_ip}:8096/Sessions/Playing/Stopped' -d '{json.dumps(playback_flicker)}' -H 'Content-Type:application/json' -H 'X-Emby-Authorization:{client_auth}, Token={client_token}'"
+        client.succeed(stop_flicker)
+        time.sleep(2)
+        client.succeed(start_cmd)
+        time.sleep(2)
+
+        # Flicker 2: stop 2s, restart 2s (total absent = 4s < 5s delay)
+        client.succeed(stop_flicker)
+        time.sleep(2)
+        client.succeed(start_cmd)
+        time.sleep(2)
+
+        # Should still be throttled — flicker gaps didn't accumulate
+        assert is_throttled(), "Should remain throttled after session flickers (contiguous absence < 5s)"
+
+        # Genuine stop: absent for full stop delay
+        client.succeed(stop_flicker)
+        time.sleep(6)
+        assert not is_throttled(), "Should unthrottle after contiguous 5s+ absence"
+
+        # Restart after genuine stop
+        client.succeed(start_cmd)
+        time.sleep(2)
+        assert is_throttled(), "Should re-throttle after restart"
+
+        # Clean up
+        client.succeed(stop_flicker)
+        time.sleep(2)
+
+    # Restore the fast-polling monitor for subsequent tests
+    server.succeed("systemctl stop monitor-flicker || true")
+    time.sleep(1)
+    server.succeed(f"""
+      systemd-run --unit=monitor-test \
+        --setenv=JELLYFIN_URL=http://localhost:8096 \
+        --setenv=JELLYFIN_API_KEY={token} \
+        --setenv=QBITTORRENT_URL=http://localhost:8080 \
+        --setenv=CHECK_INTERVAL=1 \
+        --setenv=STREAMING_START_DELAY=1 \
+        --setenv=STREAMING_STOP_DELAY=1 \
+        --setenv=TOTAL_BANDWIDTH_BUDGET=50000000 \
+        --setenv=SERVICE_BUFFER=2000000 \
+        --setenv=DEFAULT_STREAM_BITRATE=10000000 \
+        --setenv=MIN_TORRENT_SPEED=100 \
+        {python} {monitor}
+    """)
+    time.sleep(2)
     # === SERVICE RESTART TESTS ===
 
     with subtest("qBittorrent restart during throttled state re-applies throttling"):