diff --git a/csharp/Platform.Numbers.Tests/BitTests.cs b/csharp/Platform.Numbers.Tests/BitTests.cs
index 3a3079b..fc4a5ce 100644
--- a/csharp/Platform.Numbers.Tests/BitTests.cs
+++ b/csharp/Platform.Numbers.Tests/BitTests.cs
@@ -173,5 +173,122 @@ public static void BugWithLoadingConstantOf8Test()
         {
             Bit<byte>.PartialWrite(0, 1, 5, -5);
         }
+
+        [Theory]
+        [InlineData(0L, 0)]
+        [InlineData(1L, 1)]
+        [InlineData(2L, 1)]
+        [InlineData(3L, 2)]
+        [InlineData(4L, 1)]
+        [InlineData(5L, 2)]
+        [InlineData(7L, 3)]
+        [InlineData(8L, 1)]
+        [InlineData(15L, 4)]
+        [InlineData(255L, 8)]
+        [InlineData(1023L, 10)]
+        [InlineData(-1L, 64)]
+        [InlineData(long.MaxValue, 63)]
+        public static void BitCountTest(long value, int expectedCount)
+        {
+            Assert.Equal(expectedCount, Bit.Count(value));
+        }
+
+        [Fact]
+        public static void BitGenericPartialWriteWithNegativeShiftTest()
+        {
+            uint target = 0xFFFFFFFF;
+            uint source = 0b101;
+            
+            uint result = Bit<uint>.PartialWrite(target, source, -5, 3);
+            
+            // -5 becomes 32-5=27, so we write 101 at positions 27-29
+            uint expected = 0xEFFFFFFF; // 11101111111111111111111111111111
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public static void BitGenericPartialReadWithNegativeShiftTest()
+        {
+            uint target = 0xEFFFFFFF; // 11101111111111111111111111111111
+            
+            uint result = Bit<uint>.PartialRead(target, -5, 3);
+            
+            // -5 becomes 27, read 3 bits at position 27-29 should give 101
+            uint expected = 0b101;
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public static void BitGenericPartialWriteWithNegativeLimitTest()
+        {
+            uint target = 0;
+            uint source = 0b111;
+            
+            uint result = Bit<uint>.PartialWrite(target, source, 0, -29);
+            
+            uint expected = 0b111;
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public static void BitGenericPartialReadWithNegativeLimitTest()
+        {
+            uint target = 0b111;
+            
+            uint result = Bit<uint>.PartialRead(target, 0, -29);
+            
+            uint expected = 0b111;
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public static void BitGenericPartialWriteReadRoundTripTest()
+        {
+            uint original = 0b10110101;
+            uint value1 = 0b011;
+            uint value2 = 0b1010;
+            
+            uint packed = Bit<uint>.PartialWrite(original, value1, 2, 3);
+            packed = Bit<uint>.PartialWrite(packed, value2, 8, 4);
+            
+            uint extracted1 = Bit<uint>.PartialRead(packed, 2, 3);
+            uint extracted2 = Bit<uint>.PartialRead(packed, 8, 4);
+            
+            Assert.Equal(value1, extracted1);
+            Assert.Equal(value2, extracted2);
+        }
+
+        [Theory]
+        [InlineData(typeof(byte))]
+        [InlineData(typeof(ushort))]
+        [InlineData(typeof(uint))]
+        [InlineData(typeof(ulong))]
+        public static void BitGenericWorksWithDifferentTypes(Type numericType)
+        {
+            if (numericType == typeof(byte))
+            {
+                byte result = Bit<byte>.PartialWrite(0, 3, 1, 2);
+                Assert.Equal((byte)6, result);
+                Assert.Equal((byte)3, Bit<byte>.PartialRead(result, 1, 2));
+            }
+            else if (numericType == typeof(ushort))
+            {
+                ushort result = Bit<ushort>.PartialWrite(0, 3, 1, 2);
+                Assert.Equal((ushort)6, result);
+                Assert.Equal((ushort)3, Bit<ushort>.PartialRead(result, 1, 2));
+            }
+            else if (numericType == typeof(uint))
+            {
+                uint result = Bit<uint>.PartialWrite(0, 3, 1, 2);
+                Assert.Equal(6u, result);
+                Assert.Equal(3u, Bit<uint>.PartialRead(result, 1, 2));
+            }
+            else if (numericType == typeof(ulong))
+            {
+                ulong result = Bit<ulong>.PartialWrite(0, 3, 1, 2);
+                Assert.Equal(6ul, result);
+                Assert.Equal(3ul, Bit<ulong>.PartialRead(result, 1, 2));
+            }
+        }
     }
 }
diff --git a/csharp/Platform.Numbers.Tests/MathTests.cs b/csharp/Platform.Numbers.Tests/MathTests.cs
new file mode 100644
index 0000000..b5f38cd
--- /dev/null
+++ b/csharp/Platform.Numbers.Tests/MathTests.cs
@@ -0,0 +1,111 @@
+using System;
+using Xunit;
+
+namespace Platform.Numbers.Tests
+{
+    public static class MathTests
+    {
+        [Theory]
+        [InlineData(0ul, 1ul)]
+        [InlineData(1ul, 1ul)]
+        [InlineData(2ul, 2ul)]
+        [InlineData(3ul, 6ul)]
+        [InlineData(4ul, 24ul)]
+        [InlineData(5ul, 120ul)]
+        [InlineData(6ul, 720ul)]
+        [InlineData(10ul, 3628800ul)]
+        [InlineData(20ul, 2432902008176640000ul)]
+        public static void FactorialTest(ulong input, ulong expected)
+        {
+            Assert.Equal(expected, Math.Factorial(input));
+        }
+
+        [Theory]
+        [InlineData(21ul)]
+        [InlineData(100ul)]
+        [InlineData(ulong.MaxValue)]
+        public static void FactorialOutOfRangeTest(ulong input)
+        {
+            Assert.Throws<ArgumentOutOfRangeException>(() => Math.Factorial(input));
+        }
+
+        [Theory]
+        [InlineData(0ul, 1ul)]
+        [InlineData(1ul, 1ul)]
+        [InlineData(2ul, 2ul)]
+        [InlineData(3ul, 5ul)]
+        [InlineData(4ul, 14ul)]
+        [InlineData(5ul, 42ul)]
+        [InlineData(6ul, 132ul)]
+        [InlineData(10ul, 16796ul)]
+        [InlineData(36ul, 11959798385860453492ul)]
+        public static void CatalanTest(ulong input, ulong expected)
+        {
+            Assert.Equal(expected, Math.Catalan(input));
+        }
+
+        [Theory]
+        [InlineData(37ul)]
+        [InlineData(100ul)]
+        [InlineData(ulong.MaxValue)]
+        public static void CatalanOutOfRangeTest(ulong input)
+        {
+            Assert.Throws<ArgumentOutOfRangeException>(() => Math.Catalan(input));
+        }
+
+        [Theory]
+        [InlineData(0ul, true)]
+        [InlineData(1ul, true)]
+        [InlineData(2ul, true)]
+        [InlineData(3ul, false)]
+        [InlineData(4ul, true)]
+        [InlineData(5ul, false)]
+        [InlineData(8ul, true)]
+        [InlineData(16ul, true)]
+        [InlineData(32ul, true)]
+        [InlineData(64ul, true)]
+        [InlineData(128ul, true)]
+        [InlineData(256ul, true)]
+        [InlineData(512ul, true)]
+        [InlineData(1024ul, true)]
+        [InlineData(1023ul, false)]
+        [InlineData(1025ul, false)]
+        [InlineData(9ul, false)]
+        [InlineData(15ul, false)]
+        [InlineData(17ul, false)]
+        public static void IsPowerOfTwoTest(ulong input, bool expected)
+        {
+            Assert.Equal(expected, Math.IsPowerOfTwo(input));
+        }
+
+        [Fact]
+        public static void FactorialGenericTest()
+        {
+            Assert.Equal(6u, Math.Factorial(3u));
+            Assert.Equal(24ul, Math.Factorial(4ul));
+        }
+
+        [Fact]
+        public static void CatalanGenericTest()
+        {
+            Assert.Equal(5u, Math.Catalan(3u));
+            Assert.Equal(14ul, Math.Catalan(4ul));
+        }
+
+        [Fact]
+        public static void IsPowerOfTwoGenericTest()
+        {
+            Assert.True(Math.IsPowerOfTwo(8u));
+            Assert.False(Math.IsPowerOfTwo(9u));
+            Assert.True(Math.IsPowerOfTwo(16ul));
+            Assert.False(Math.IsPowerOfTwo(15ul));
+        }
+
+        [Fact]
+        public static void MaximumConstantsTest()
+        {
+            Assert.Equal(20ul, Math.MaximumFactorialNumber);
+            Assert.Equal(36ul, Math.MaximumCatalanIndex);
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/Platform.Numbers/Math.cs b/csharp/Platform.Numbers/Math.cs
index 84a48b7..8c085bf 100644
--- a/csharp/Platform.Numbers/Math.cs
+++ b/csharp/Platform.Numbers/Math.cs
@@ -52,7 +52,7 @@ public static class Math
         /// </returns>
         public static TLinkAddress Factorial<TLinkAddress>(TLinkAddress n) where TLinkAddress : IUnsignedNumber<TLinkAddress>, IComparisonOperators<TLinkAddress, TLinkAddress, bool>
         {
-            if (n >= TLinkAddress.Zero && n <= TLinkAddress.CreateTruncating(MaximumCatalanIndex))
+            if (n >= TLinkAddress.Zero && n <= TLinkAddress.CreateTruncating(MaximumFactorialNumber))
             {
                 return TLinkAddress.CreateTruncating(_factorials[ulong.CreateTruncating(n)]);
             }