diff --git a/tests/unit/test_ttm_analysis.py b/tests/unit/test_ttm_analysis.py
index 224fe932..f4f4106c 100644
--- a/tests/unit/test_ttm_analysis.py
+++ b/tests/unit/test_ttm_analysis.py
@@ -174,6 +174,25 @@ class TestComputeTTMMetrics:
         expected_yoy = ((1.05 ** 4) - 1) * 100
         assert abs(yoy - expected_yoy) < 0.5
 
+    def test_revenue_yoy_with_exactly_5_quarters(self):
+        """YoY is available when exactly 5 quarters exist (minimum for 4-quarter lookback)."""
+        result = self.compute(
+            _make_income_csv(5), _make_balance_csv(5), _make_cashflow_csv(5)
+        )
+        yoy = result["trends"]["revenue_yoy_pct"]
+        assert yoy is not None
+        # quarterly[-5] vs quarterly[-1] with 5% QoQ → 1.05^4 - 1 ≈ 21.55%
+        expected_yoy = ((1.05 ** 4) - 1) * 100
+        assert abs(yoy - expected_yoy) < 0.5
+
+    def test_revenue_yoy_none_with_4_quarters(self):
+        """YoY should be None when fewer than 5 quarters are available."""
+        result = self.compute(
+            _make_income_csv(4), _make_balance_csv(4), _make_cashflow_csv(4)
+        )
+        yoy = result["trends"]["revenue_yoy_pct"]
+        assert yoy is None
+
     def test_margin_trend_expanding(self):
         """Expanding margin should be detected."""
         # Create data where net margin expands over time