Improve backtest lazy loading and test automation

tests/test_databento_source.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import os
 import tempfile
 from datetime import date, timedelta
 from pathlib import Path
@@ -306,3 +307,20 @@ class TestDatabentoHistoricalPriceSourceIntegration:
         assert stats["total_size_bytes"] > 0
         assert len(stats["entries"]) == 1
         assert stats["entries"][0]["symbol"] == "GLD"
+
+
+@pytest.mark.skipif(not os.getenv("DATABENTO_API_KEY"), reason="requires DATABENTO_API_KEY")
+def test_live_databento_source_loads_recent_gld_daily_bars(temp_cache_dir: Path) -> None:
+    source = DatabentoHistoricalPriceSource(
+        config=DatabentoSourceConfig(
+            api_key=os.getenv("DATABENTO_API_KEY"),
+            cache_dir=temp_cache_dir,
+            schema="ohlcv-1d",
+        )
+    )
+
+    points = source.load_daily_closes("GLD", date(2024, 7, 1), date(2024, 7, 5))
+
+    assert len(points) >= 4
+    assert points[0].date == date(2024, 7, 1)
+    assert points[0].close > 0