From a1130ea43bf9df7718fdec5e27fa4f6bd33cf151 Mon Sep 17 00:00:00 2001
From: ao gong <41768719+ageorge156@users.noreply.github.com>
Date: Fri, 21 Aug 2026 21:24:03 +0800
Subject: [PATCH] test: reject ambiguous duplicate rebalance dates

---
 tests/test_portfolio_construction.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tests/test_portfolio_construction.py b/tests/test_portfolio_construction.py
index 43cd606..32756d2 100644
--- a/tests/test_portfolio_construction.py
+++ b/tests/test_portfolio_construction.py
@@ -130,6 +130,17 @@ def test_portfolio_construction_rejects_duplicate_assets() -> None:
         scores_to_target_weights(duplicate_scores, top_k=1)
 
 
+def test_weight_table_rejects_duplicate_rebalance_dates() -> None:
+    duplicate_date = pd.Timestamp("2026-01-05")
+    scores = pd.DataFrame(
+        {"A": [1.0, 2.0]},
+        index=[duplicate_date, duplicate_date],
+    )
+
+    with pytest.raises(ValueError, match="unique rebalance dates"):
+        scores_to_weight_table(scores, top_k=1)
+
+
 def test_weight_table_rejects_non_numeric_scores() -> None:
     scores = pd.DataFrame({"A": ["high"], "B": ["low"]})