diff --git a/tests/test_factor_attribution.py b/tests/test_factor_attribution.py
index a259834..3437a76 100644
--- a/tests/test_factor_attribution.py
+++ b/tests/test_factor_attribution.py
@@ -316,6 +316,48 @@ class LocalFactorConstructionTests(unittest.TestCase):
         self.assertTrue(factors.iloc[260:].notna().all().all())
         self.assertGreater(factors.iloc[260:].abs().sum().sum(), 0.0)
 
+    def test_build_extension_factors_does_not_use_future_prices(self):
+        prices = self._make_price_frame(benchmark="SPY")
+        mutated = prices.copy()
+        future_start = prices.index[280]
+        mutated.loc[future_start:, "A"] = mutated.loc[future_start:, "A"] * 1.8
+        mutated.loc[future_start:, "B"] = mutated.loc[future_start:, "B"] * 0.4
+
+        original = build_extension_factors(prices, benchmark="SPY", market="us")
+        changed = build_extension_factors(mutated, benchmark="SPY", market="us")
+
+        comparison_end = prices.index[279]
+        pd.testing.assert_frame_equal(original.loc[:comparison_end], changed.loc[:comparison_end])
+        self.assertGreater(
+            (original.loc[future_start:] - changed.loc[future_start:]).abs().sum().sum(),
+            0.0,
+        )
+
+    def test_build_proxy_core_factors_does_not_use_future_prices(self):
+        prices = self._make_price_frame(benchmark="000300.SS")
+        mutated = prices.copy()
+        future_start = prices.index[280]
+        mutated.loc[future_start:, "C"] = mutated.loc[future_start:, "C"] * 0.35
+        mutated.loc[future_start:, "D"] = mutated.loc[future_start:, "D"] * 1.6
+
+        original = build_proxy_core_factors(prices, benchmark="000300.SS", market="cn")
+        changed = build_proxy_core_factors(mutated, benchmark="000300.SS", market="cn")
+
+        comparison_end = prices.index[279]
+        pd.testing.assert_frame_equal(original.loc[:comparison_end], changed.loc[:comparison_end])
+        self.assertGreater(
+            (original.loc[future_start:] - changed.loc[future_start:]).abs().sum().sum(),
+            0.0,
+        )
+
+    def test_build_proxy_core_factors_falls_back_to_equal_weight_market_when_benchmark_missing(self):
+        prices = self._make_price_frame(benchmark="CN_BENCH").drop(columns=["CN_BENCH"])
+
+        factors = build_proxy_core_factors(prices, benchmark="000300.SS", market="cn")
+
+        expected_market = prices.pct_change().mean(axis=1)
+        pd.testing.assert_series_equal(factors["MKT"], expected_market, check_names=False)
+
     def _make_price_frame(self, benchmark: str) -> pd.DataFrame:
         dates = pd.date_range("2025-01-01", periods=320, freq="B")
         steps = np.arange(len(dates), dtype=float)