wip: estado de trabajo pendiente antes de la vista grid (suite 230 verde)

tests/test_store_sync_watermark.py

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+"""Store-side support for incremental sync: the known-id boundary and the
+watermark that survives a re-discovery."""
+from __future__ import annotations
+
+from yt_scraper.store import Store, VideoRef
+
+
+def _store(tmp_path) -> Store:
+    store = Store(tmp_path / "state.db")
+    store.upsert_channel("UC1", "@alpha", "Alpha", 0)
+    return store
+
+
+def test_known_video_ids_is_scoped_to_the_channel(tmp_path):
+    store = _store(tmp_path)
+    store.upsert_channel("UC2", "@beta", "Beta", 0)
+    store.upsert_videos([
+        VideoRef("a", "UC1", "A", "https://y/watch?v=a"),
+        VideoRef("b", "UC1", "B", "https://y/watch?v=b"),
+        VideoRef("c", "UC2", "C", "https://y/watch?v=c"),
+    ])
+
+    assert store.known_video_ids("UC1") == {"a", "b"}
+    assert store.known_video_ids("UC2") == {"c"}
+    assert store.known_video_ids("nope") == set()
+
+
+def test_rediscovery_does_not_wipe_a_known_upload_date(tmp_path):
+    """Flat discovery reports upload_date=None; without COALESCE a routine sync
+    would erase the dates learned during extraction — and with them the very
+    watermark this feature is built on."""
+    store = _store(tmp_path)
+    store.upsert_videos([VideoRef("a", "UC1", "A", "https://y/watch?v=a", "20260715", 120)])
+
+    store.upsert_videos([VideoRef("a", "UC1", "A (renamed)", "https://y/watch?v=a", None, None)])
+
+    row = store.get_video("a")
+    assert row.upload_date == "20260715"
+    assert row.duration == 120
+    assert row.title == "A (renamed)", "titles should still refresh"
+
+
+def test_latest_upload_date_ignores_undated_rows(tmp_path):
+    store = _store(tmp_path)
+    store.upsert_videos([
+        VideoRef("a", "UC1", "A", "https://y/watch?v=a", "20260101"),
+        VideoRef("b", "UC1", "B", "https://y/watch?v=b", None),
+        VideoRef("c", "UC1", "C", "https://y/watch?v=c", "20260720"),
+    ])
+
+    assert store.latest_upload_date("UC1") == "20260720"
+
+
+def test_mark_channel_synced_recounts_instead_of_trusting_the_window(tmp_path):
+    """An incremental pass only sees the newest slice, so video_count must come
+    from the DB — otherwise an 848-video channel shrinks to the window size."""
+    store = _store(tmp_path)
+    store.upsert_videos([
+        VideoRef(f"v{i}", "UC1", f"V{i}", f"https://y/watch?v=v{i}", "20260101")
+        for i in range(40)
+    ])
+
+    marks = store.mark_channel_synced("UC1")
+
+    assert marks["video_count"] == 40
+    channel = store.get_channel("UC1")
+    assert channel["video_count"] == 40
+    assert channel["last_video_date"] == "20260101"
+    assert channel["last_synced_at"]
+
+
+def test_mark_channel_synced_keeps_the_last_date_when_nothing_is_dated(tmp_path):
+    store = _store(tmp_path)
+    store.upsert_videos([VideoRef("a", "UC1", "A", "https://y/watch?v=a", "20260101")])
+    store.mark_channel_synced("UC1")
+
+    store.upsert_videos([VideoRef("b", "UC1", "B", "https://y/watch?v=b", None)])
+    store.mark_channel_synced("UC1")
+
+    assert store.get_channel("UC1")["last_video_date"] == "20260101"