Add UT Neo.Extensions

src/Neo.Extensions/BigIntegerExtensions.cs

@@ -43,6 +43,11 @@ public static BigInteger Mod(this BigInteger x, BigInteger y)
 
         public static BigInteger ModInverse(this BigInteger a, BigInteger n)
         {
+            if (BigInteger.GreatestCommonDivisor(a, n) != 1)
+            {
+                throw new ArithmeticException("No modular inverse exists for the given inputs.");
+            }
+
             BigInteger i = n, v = 0, d = 1;
             while (a > 0)
             {

tests/Neo.Extensions.Tests/UT_BigIntegerExtensions.cs

@@ -11,6 +11,8 @@
 
 using FluentAssertions;
 using Neo.Extensions;
+using System;
+using System.Collections.Generic;
 using System.Numerics;
 
 namespace Neo.Extensions.Tests
@@ -32,16 +34,79 @@ public void TestGetLowestSetBit()
 
             var big4 = new BigInteger(long.MinValue);
             big4.GetLowestSetBit().Should().Be(63);
+
+            var big5 = new BigInteger(-18);
+            big5.GetLowestSetBit().Should().Be(1);
+
+            var big6 = BigInteger.Pow(2, 1000);
+            big6.GetLowestSetBit().Should().Be(1000);
         }
 
         [TestMethod]
         public void TestToByteArrayStandard()
         {
             BigInteger number = BigInteger.Zero;
-            Assert.AreEqual("", number.ToByteArrayStandard().ToHexString());
+            number.ToByteArrayStandard().Should().BeEmpty();
 
             number = BigInteger.One;
-            Assert.AreEqual("01", number.ToByteArrayStandard().ToHexString());
+            number.ToByteArrayStandard().Should().Equal(new byte[] { 0x01 });
+
+            number = new BigInteger(256); // Binary: 100000000
+            number.ToByteArrayStandard().Should().Equal(new byte[] { 0x00, 0x01 });
+        }
+
+        [TestMethod]
+        public void TestMod()
+        {
+            var x = new BigInteger(-13);
+            var y = new BigInteger(5);
+            var result = x.Mod(y);
+            result.Should().Be(2); // -13 % 5 is -3, but Mod method should return 2
+        }
+
+        [TestMethod]
+        public void TestModInverse()
+        {
+            var a = new BigInteger(3);
+            var n = new BigInteger(11);
+            var result = a.ModInverse(n);
+            result.Should().Be(4); // 3 * 4 % 11 == 1
+
+            a = new BigInteger(1);
+            n = new BigInteger(11);
+            result = a.ModInverse(n);
+            result.Should().Be(1); // 1 * 1 % 11 == 1
+
+            a = new BigInteger(13);
+            n = new BigInteger(11);
+            result = a.ModInverse(n);
+            result.Should().Be(6); // 13 % 11 = 2, and 2 * 6 % 11 == 1
+
+            a = new BigInteger(6);
+            n = new BigInteger(12); // 6 and 12 are not coprime
+            Action act = () => a.ModInverse(n);
+            act.Should().Throw<ArithmeticException>()
+               .WithMessage("No modular inverse exists for the given inputs.");
+        }
+
+        [TestMethod]
+        public void TestBit()
+        {
+            var bigInteger = new BigInteger(5); // Binary: 101
+            var result = bigInteger.TestBit(2);
+            result.Should().BeTrue(); // Bit at index 2 is set (1)
+
+            bigInteger = new BigInteger(5); // Binary: 101
+            result = bigInteger.TestBit(1);
+            result.Should().BeFalse(); // Bit at index 1 is not set (0)
+        }
+
+        [TestMethod]
+        public void TestSum()
+        {
+            var bigIntegers = new List<BigInteger> { 1, 2, 3, 4 };
+            var result = bigIntegers.Sum();
+            result.Should().Be(10);
         }
     }
 }

tests/Neo.Extensions.Tests/UT_ByteExtensions.cs

@@ -33,5 +33,29 @@ public void TestToHexString()
             str1.ToHexString(false).Should().Be("6e656f");
             str1.ToHexString(true).Should().Be("6f656e");
         }
+
+        [TestMethod]
+        public void TestReadOnlySpanToHexString()
+        {
+            byte[] input = { 0x0F, 0xA4, 0x3B };
+            var span = new ReadOnlySpan<byte>(input);
+            string result = span.ToHexString();
+            result.Should().Be("0fa43b");
+
+            input = Array.Empty<byte>();
+            span = new ReadOnlySpan<byte>(input);
+            result = span.ToHexString();
+            result.Should().BeEmpty();
+
+            input = new byte[] { 0x5A };
+            span = new ReadOnlySpan<byte>(input);
+            result = span.ToHexString();
+            result.Should().Be("5a");
+
+            input = new byte[] { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF };
+            span = new ReadOnlySpan<byte>(input);
+            result = span.ToHexString();
+            result.Should().Be("0123456789abcdef");
+        }
     }
 }