Added some unit tests

Author: Sergio0694

UnitTests/UnitTests.HighPerformance.Shared/Extensions/Test_MemoryExtensions.cs

@@ -4,6 +4,8 @@
 
 using System;
 using System.IO;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using Microsoft.Toolkit.HighPerformance.Extensions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
@@ -12,6 +14,109 @@ namespace UnitTests.HighPerformance.Extensions
     [TestClass]
     public class Test_MemoryExtensions
     {
+        [TestCategory("MemoryExtensions")]
+        [TestMethod]
+        public void Test_MemoryExtensions_Cast_Empty()
+        {
+            Memory<byte> m1 = default;
+            Memory<byte> mc1 = m1.Cast<byte, byte>();
+
+            Assert.IsTrue(mc1.IsEmpty);
+
+            Memory<byte> m2 = default;
+            Memory<float> mc2 = m2.Cast<byte, float>();
+
+            Assert.IsTrue(mc2.IsEmpty);
+
+            Memory<short> m3 = default;
+            Memory<Guid> mc3 = m3.Cast<short, Guid>();
+
+            Assert.IsTrue(mc3.IsEmpty);
+
+            Memory<byte> m4 = new byte[12].AsMemory(12);
+            Memory<int> mc4 = m4.Cast<byte, int>();
+
+            Assert.IsTrue(mc4.IsEmpty);
+
+            Memory<byte> m5 = new byte[12].AsMemory().Slice(4).Slice(8);
+            Memory<int> mc5 = m5.Cast<byte, int>();
+
+            Assert.IsTrue(mc5.IsEmpty);
+        }
+
+        [TestCategory("MemoryExtensions")]
+        [TestMethod]
+        public void Test_MemoryExtensions_Cast_TooShort()
+        {
+            Memory<byte> m1 = new byte[3];
+            Memory<int> mc1 = m1.Cast<byte, int>();
+
+            Assert.IsTrue(mc1.IsEmpty);
+
+            Memory<byte> m2 = new byte[13];
+            Memory<float> mc2 = m2.Cast<byte, float>();
+
+            Assert.AreEqual(mc2.Length, 3);
+
+            Memory<byte> m3 = new byte[16].AsMemory(5);
+            Memory<float> mc3 = m3.Cast<byte, float>();
+
+            Assert.AreEqual(mc3.Length, 2);
+        }
+
+        [TestCategory("MemoryExtensions")]
+        [TestMethod]
+        public void Test_MemoryExtensions_FromArray_CastFromByte()
+        {
+            Memory<byte> memoryOfBytes = new byte[128];
+            Memory<float> memoryOfFloats = memoryOfBytes.Cast<byte, float>();
+
+            Assert.AreEqual(memoryOfFloats.Length, 128 / sizeof(float));
+
+            Span<byte> spanOfBytes = memoryOfBytes.Span;
+            Span<float> spanOfFloats = memoryOfFloats.Span;
+
+            Assert.IsTrue(Unsafe.AreSame(
+                ref spanOfBytes[0],
+                ref Unsafe.As<float, byte>(ref spanOfFloats[0])));
+        }
+
+        [TestCategory("MemoryExtensions")]
+        [TestMethod]
+        public void Test_MemoryExtensions_FromArray_CastToByte()
+        {
+            Memory<float> memoryOfFloats = new float[128];
+            Memory<byte> memoryOfBytes = memoryOfFloats.Cast<float, byte>();
+
+            Assert.AreEqual(memoryOfBytes.Length, 128 * sizeof(float));
+
+            Span<float> spanOfFloats = memoryOfFloats.Span;
+            Span<byte> spanOfBytes = memoryOfBytes.Span;
+
+            Assert.IsTrue(Unsafe.AreSame(
+                ref spanOfFloats[0],
+                ref Unsafe.As<byte, float>(ref spanOfBytes[0])));
+        }
+
+        [TestCategory("MemoryExtensions")]
+        [TestMethod]
+        public void Test_MemoryExtensions_FromArray_CastFromByteAndBack()
+        {
+            var data = new byte[128];
+            Memory<byte> memoryOfBytes = data;
+            Memory<float> memoryOfFloats = memoryOfBytes.Cast<byte, float>();
+            Memory<byte> memoryBack = memoryOfFloats.Cast<float, byte>();
+
+            Assert.AreEqual(memoryOfBytes.Length, memoryBack.Length);
+
+            Assert.IsTrue(MemoryMarshal.TryGetArray<byte>(memoryBack, out var segment));
+            Assert.AreSame(segment.Array!, data);
+            Assert.AreEqual(segment.Offset, 0);
+            Assert.AreEqual(segment.Count, data.Length);
+
+            Assert.IsTrue(memoryOfBytes.Equals(memoryBack));
+        }
+
         [TestCategory("MemoryExtensions")]
         [TestMethod]
         public void Test_MemoryExtensions_EmptyMemoryStream()