diff --git a/X10D.Tests/src/Core/SpanTest.cs b/X10D.Tests/src/Core/SpanTest.cs
index a92befd..1c86feb 100644
--- a/X10D.Tests/src/Core/SpanTest.cs
+++ b/X10D.Tests/src/Core/SpanTest.cs
@@ -1,4 +1,4 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 using X10D.Collections;
 using X10D.Core;
 
@@ -7,6 +7,142 @@ namespace X10D.Tests.Core;
 [TestClass]
 public class SpanTest
 {
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenReadOnlySpanWithNoMatchingElements_UsingByteEnum()
+    {
+        ReadOnlySpan<EnumByte> span = stackalloc EnumByte[1] {EnumByte.B};
+
+        Assert.IsFalse(span.Contains(EnumByte.A));
+        Assert.IsFalse(span.Contains(EnumByte.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenReadOnlySpanWithNoMatchingElements_UsingInt16Enum()
+    {
+        ReadOnlySpan<EnumInt16> span = stackalloc EnumInt16[1] {EnumInt16.B};
+
+        Assert.IsFalse(span.Contains(EnumInt16.A));
+        Assert.IsFalse(span.Contains(EnumInt16.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenReadOnlySpanWithNoMatchingElements_UsingInt32Enum()
+    {
+        ReadOnlySpan<EnumInt32> span = stackalloc EnumInt32[1] {EnumInt32.B};
+
+        Assert.IsFalse(span.Contains(EnumInt32.A));
+        Assert.IsFalse(span.Contains(EnumInt32.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenReadOnlySpanWithNoMatchingElements_UsingInt64Enum()
+    {
+        ReadOnlySpan<EnumInt64> span = stackalloc EnumInt64[1] {EnumInt64.B};
+
+        Assert.IsFalse(span.Contains(EnumInt64.A));
+        Assert.IsFalse(span.Contains(EnumInt64.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenReadOnlySpanWithMatchingElements_UsingByteEnum()
+    {
+        ReadOnlySpan<EnumByte> span = stackalloc EnumByte[1] {EnumByte.B};
+
+        Assert.IsTrue(span.Contains(EnumByte.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenReadOnlySpanWithMatchingElements_UsingInt16Enum()
+    {
+        ReadOnlySpan<EnumInt16> span = stackalloc EnumInt16[1] {EnumInt16.B};
+
+        Assert.IsTrue(span.Contains(EnumInt16.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenReadOnlySpanWithMatchingElements_UsingInt32Enum()
+    {
+        ReadOnlySpan<EnumInt32> span = stackalloc EnumInt32[1] {EnumInt32.B};
+
+        Assert.IsTrue(span.Contains(EnumInt32.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenReadOnlySpanWithMatchingElements_UsingInt64Enum()
+    {
+        ReadOnlySpan<EnumInt64> span = stackalloc EnumInt64[1] {EnumInt64.B};
+
+        Assert.IsTrue(span.Contains(EnumInt64.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenSpanWithNoMatchingElements_UsingByteEnum()
+    {
+        Span<EnumByte> span = stackalloc EnumByte[1] {EnumByte.B};
+
+        Assert.IsFalse(span.Contains(EnumByte.A));
+        Assert.IsFalse(span.Contains(EnumByte.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenSpanWithNoMatchingElements_UsingInt16Enum()
+    {
+        Span<EnumInt16> span = stackalloc EnumInt16[1] {EnumInt16.B};
+
+        Assert.IsFalse(span.Contains(EnumInt16.A));
+        Assert.IsFalse(span.Contains(EnumInt16.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenSpanWithNoMatchingElements_UsingInt32Enum()
+    {
+        Span<EnumInt32> span = stackalloc EnumInt32[1] {EnumInt32.B};
+
+        Assert.IsFalse(span.Contains(EnumInt32.A));
+        Assert.IsFalse(span.Contains(EnumInt32.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnFalse_GivenSpanWithNoMatchingElements_UsingInt64Enum()
+    {
+        Span<EnumInt64> span = stackalloc EnumInt64[1] {EnumInt64.B};
+
+        Assert.IsFalse(span.Contains(EnumInt64.A));
+        Assert.IsFalse(span.Contains(EnumInt64.C));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenSpanWithMatchingElements_UsingByteEnum()
+    {
+        Span<EnumByte> span = stackalloc EnumByte[1] {EnumByte.B};
+
+        Assert.IsTrue(span.Contains(EnumByte.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenSpanWithMatchingElements_UsingInt16Enum()
+    {
+        Span<EnumInt16> span = stackalloc EnumInt16[1] {EnumInt16.B};
+
+        Assert.IsTrue(span.Contains(EnumInt16.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenSpanWithMatchingElements_UsingInt32Enum()
+    {
+        Span<EnumInt32> span = stackalloc EnumInt32[1] {EnumInt32.B};
+
+        Assert.IsTrue(span.Contains(EnumInt32.B));
+    }
+
+    [TestMethod]
+    public void Contains_ShouldReturnTrue_GivenSpanWithMatchingElements_UsingInt64Enum()
+    {
+        Span<EnumInt64> span = stackalloc EnumInt64[1] {EnumInt64.B};
+
+        Assert.IsTrue(span.Contains(EnumInt64.B));
+    }
+
     [TestMethod]
     public void Pack8Bit_Should_Pack_Correctly()
     {
@@ -96,4 +232,32 @@ public class SpanTest
 
         Assert.AreEqual(value, unpacks.PackInt64());
     }
+
+    private enum EnumByte : byte
+    {
+        A,
+        B,
+        C
+    }
+
+    private enum EnumInt16 : short
+    {
+        A,
+        B,
+        C
+    }
+
+    private enum EnumInt32
+    {
+        A,
+        B,
+        C
+    }
+
+    private enum EnumInt64 : long
+    {
+        A,
+        B,
+        C
+    }
 }
diff --git a/X10D/src/Core/SpanExtensions.cs b/X10D/src/Core/SpanExtensions.cs
index 3d6133d..bc5cb1d 100644
--- a/X10D/src/Core/SpanExtensions.cs
+++ b/X10D/src/Core/SpanExtensions.cs
@@ -121,12 +121,16 @@ public static class SpanExtensions
                         return MemoryMarshal.CreateSpan(ref enums, span.Length).Contains(Unsafe.As<T, ulong>(ref value));
                     }
 
+                // dotcover disable
+                //NOSONAR
                 default:
 #if NET7_0_OR_GREATER
                     throw new UnreachableException($"Enum with the size of {Unsafe.SizeOf<T>()} bytes is unexpected.");
 #else
                     throw new ArgumentException($"Enum with the size of {Unsafe.SizeOf<T>()} bytes is unexpected.");
 #endif
+                //NOSONAR
+                // dotcover enable
             }
         }
 #else