test(dotnet): cover factor calculator input ordering

src/dotnet/QuantEngine.Core.Tests/FactorCalculatorTests.cs

@@ -109,5 +109,21 @@ namespace QuantEngine.Core.Tests
 
             Assert.Equal(expectedStDev, outputs.StDev20D, 5);
         }
+
+        [Fact]
+        public void CalculateFactors_UnsortedInput_ProducesSameOutputs()
+        {
+            var stock = CreateMockBars("005930", 100.0, 1.0, 130);
+            var index = CreateMockBars("KOSPI", 2000.0, 0.0, 130);
+
+            stock.Reverse();
+            index.Reverse();
+
+            var outputs = FactorCalculator.CalculateFactors(stock, index);
+
+            double expectedMom20 = (20.0 / 209.0) * 100.0;
+            Assert.Equal(expectedMom20, outputs.Momentum20D, 5);
+            Assert.Equal(1.0, outputs.Beta60D);
+        }
     }
 }