add option for following nightly yt-dlp releases (closes #999)

app/tests/test_nightly_update.py

@@ -0,0 +1,29 @@
+"""Tests for nightly yt-dlp update scheduling helpers."""
+
+from __future__ import annotations
+
+import unittest
+from datetime import datetime
+
+from main import seconds_until_next_daily_time
+
+
+class NightlyUpdateTests(unittest.TestCase):
+    def test_seconds_until_later_today(self):
+        now = datetime(2026, 6, 4, 10, 0, 0)
+        delay = seconds_until_next_daily_time("15:30", now)
+        self.assertEqual(delay, 5 * 3600 + 30 * 60)
+
+    def test_seconds_until_wraps_to_next_day(self):
+        now = datetime(2026, 6, 4, 18, 0, 0)
+        delay = seconds_until_next_daily_time("04:00", now)
+        self.assertEqual(delay, 10 * 3600)
+
+    def test_seconds_until_same_minute_is_next_day(self):
+        now = datetime(2026, 6, 4, 4, 0, 30)
+        delay = seconds_until_next_daily_time("04:00", now)
+        self.assertAlmostEqual(delay, 24 * 3600 - 30, delta=1)
+
+
+if __name__ == "__main__":
+    unittest.main()