test: reject unsorted rebalance dates

tests/test_portfolio_construction.py

@@ -141,6 +141,16 @@ def test_weight_table_rejects_duplicate_rebalance_dates() -> None:
         scores_to_weight_table(scores, top_k=1)
 
 
+def test_weight_table_rejects_unsorted_rebalance_dates() -> None:
+    scores = pd.DataFrame(
+        {"A": [1.0, 2.0]},
+        index=pd.to_datetime(["2026-01-07", "2026-01-05"]),
+    )
+
+    with pytest.raises(ValueError, match="chronological order"):
+        scores_to_weight_table(scores, top_k=1)
+
+
 def test_weight_table_rejects_non_numeric_scores() -> None:
     scores = pd.DataFrame({"A": ["high"], "B": ["low"]})