diff --git a/X10D.Tests/src/Core/SpanTest.cs b/X10D.Tests/src/Core/SpanTest.cs
index c5e27a4..e242c12 100644
--- a/X10D.Tests/src/Core/SpanTest.cs
+++ b/X10D.Tests/src/Core/SpanTest.cs
@@ -146,6 +146,46 @@ public class SpanTest
         Assert.IsTrue(span.Contains(EnumInt64.B));
     }
 
+    [TestMethod]
+    public void PackByte_ShouldThrowArgumentException_GivenSpanLengthGreaterThan8()
+    {
+        Assert.ThrowsException<ArgumentException>(() =>
+        {
+            Span<bool> span = stackalloc bool[9];
+            return span.PackByte();
+        });
+    }
+
+    [TestMethod]
+    public void PackInt16_ShouldThrowArgumentException_GivenSpanLengthGreaterThan16()
+    {
+        Assert.ThrowsException<ArgumentException>(() =>
+        {
+            Span<bool> span = stackalloc bool[17];
+            return span.PackInt16();
+        });
+    }
+
+    [TestMethod]
+    public void PackInt32_ShouldThrowArgumentException_GivenSpanLengthGreaterThan32()
+    {
+        Assert.ThrowsException<ArgumentException>(() =>
+        {
+            Span<bool> span = stackalloc bool[33];
+            return span.PackInt32();
+        });
+    }
+
+    [TestMethod]
+    public void PackInt64_ShouldThrowArgumentException_GivenSpanLengthGreaterThan64()
+    {
+        Assert.ThrowsException<ArgumentException>(() =>
+        {
+            Span<bool> span = stackalloc bool[65];
+            return span.PackInt64();
+        });
+    }
+
     [TestMethod]
     public void PackByteInternal_Fallback_ShouldReturnCorrectByte_GivenReadOnlySpan_Using()
     {
@@ -315,7 +355,7 @@ public class SpanTest
 #endif
 
     [TestMethod]
-    public void PackInt32_ShouldReturnSameAsPackByte_WhenSpanHasLength8()
+    public void PackInt32_ShouldReturnSameAsPackByte_WhenSpanHasLength8_UsingReadOnlySpan()
     {
         ReadOnlySpan<bool> span = stackalloc bool[8] {true, true, false, false, true, true, false, false};
 
@@ -326,7 +366,18 @@ public class SpanTest
     }
 
     [TestMethod]
-    public void PackInt32_ShouldReturnSameAsPackInt16_WhenSpanHasLength16()
+    public void PackInt32_ShouldReturnSameAsPackByte_WhenSpanHasLength8_UsingSpan()
+    {
+        Span<bool> span = stackalloc bool[8] {true, true, false, false, true, true, false, false};
+
+        int expected = span.PackByte();
+        int actual = span.PackInt32();
+
+        Assert.AreEqual(expected, actual);
+    }
+
+    [TestMethod]
+    public void PackInt32_ShouldReturnSameAsPackInt16_WhenSpanHasLength16_UsingReadOnlySpan()
     {
         ReadOnlySpan<bool> span = stackalloc bool[16]
         {
@@ -339,6 +390,20 @@ public class SpanTest
         Assert.AreEqual(expected, actual);
     }
 
+    [TestMethod]
+    public void PackInt32_ShouldReturnSameAsPackInt16_WhenSpanHasLength16_UsingSpan()
+    {
+        Span<bool> span = stackalloc bool[16]
+        {
+            false, false, true, false, true, false, true, true, true, false, true, true, false, true, false, false,
+        };
+
+        int expected = span.PackInt16();
+        int actual = span.PackInt32();
+
+        Assert.AreEqual(expected, actual);
+    }
+
     [TestMethod]
     public void PackInt64_ShouldReturnCorrectInt64_GivenReadOnlySpan()
     {
@@ -357,7 +422,24 @@ public class SpanTest
     }
 
     [TestMethod]
-    public void PackInt64_ShouldReturnSameAsPackByte_WhenSpanHasLength8()
+    public void PackInt64_ShouldReturnCorrectInt64_GivenSpan()
+    {
+        const long expected = 0b01010101_11010110_01101001_11010110_00010010_10010111_00101100_10100101;
+        Span<bool> span = stackalloc bool[64]
+        {
+            true, false, true, false, false, true, false, true, false, false, true, true, false, true, false, false, true,
+            true, true, false, true, false, false, true, false, true, false, false, true, false, false, false, false, true,
+            true, false, true, false, true, true, true, false, false, true, false, true, true, false, false, true, true,
+            false, true, false, true, true, true, false, true, false, true, false, true, false,
+        };
+
+        long actual = span.PackInt64();
+
+        Assert.AreEqual(expected, actual);
+    }
+
+    [TestMethod]
+    public void PackInt64_ShouldReturnSameAsPackByte_WhenSpanHasLength8_UsingReadOnlySpan()
     {
         ReadOnlySpan<bool> span = stackalloc bool[8] {true, true, false, false, true, true, false, false};
 
@@ -368,7 +450,18 @@ public class SpanTest
     }
 
     [TestMethod]
-    public void PackInt64_ShouldReturnSameAsPackInt16_WhenSpanHasLength16()
+    public void PackInt64_ShouldReturnSameAsPackByte_WhenSpanHasLength8_UsingSpan()
+    {
+        Span<bool> span = stackalloc bool[8] {true, true, false, false, true, true, false, false};
+
+        long expected = span.PackByte();
+        long actual = span.PackInt64();
+
+        Assert.AreEqual(expected, actual);
+    }
+
+    [TestMethod]
+    public void PackInt64_ShouldReturnSameAsPackInt16_WhenSpanHasLength16_UsingReadOnlySpan()
     {
         ReadOnlySpan<bool> span = stackalloc bool[16]
         {
@@ -382,7 +475,21 @@ public class SpanTest
     }
 
     [TestMethod]
-    public void PackInt64_ShouldReturnSameAsPackInt32_WhenSpanHasLength16()
+    public void PackInt64_ShouldReturnSameAsPackInt16_WhenSpanHasLength16_UsingSpan()
+    {
+        Span<bool> span = stackalloc bool[16]
+        {
+            false, false, true, false, true, false, true, true, true, false, true, true, false, true, false, false,
+        };
+
+        long expected = span.PackInt16();
+        long actual = span.PackInt64();
+
+        Assert.AreEqual(expected, actual);
+    }
+
+    [TestMethod]
+    public void PackInt64_ShouldReturnSameAsPackInt32_WhenSpanHasLength16_UsingReadOnlySpan()
     {
         ReadOnlySpan<bool> span = stackalloc bool[32]
         {
@@ -396,6 +503,43 @@ public class SpanTest
         Assert.AreEqual(expected, actual);
     }
 
+    [TestMethod]
+    public void PackInt64_ShouldReturnSameAsPackInt32_WhenSpanHasLength16_UsingSpan()
+    {
+        Span<bool> span = stackalloc bool[32]
+        {
+            false, true, false, true, false, true, false, true, true, false, true, false, true, false, true, false, false,
+            true, false, true, false, true, false, true, true, false, true, false, true, false, true, false,
+        };
+
+        long expected = span.PackInt32();
+        long actual = span.PackInt64();
+
+        Assert.AreEqual(expected, actual);
+    }
+
+    [TestMethod]
+    public void PackInt64_ShouldFallbackAndReturnCorrectValue_GivenNonPowerOfTwoLength_UsingReadOnlySpan()
+    {
+        const long expected = 0b00000000_00000000_00000000_00000000_00000000_00000000_00000001_01010011;
+        ReadOnlySpan<bool> span = stackalloc bool[10] {true, true, false, false, true, false, true, false, true, false};
+
+        long actual = span.PackInt64();
+
+        Assert.AreEqual(expected, actual);
+    }
+
+    [TestMethod]
+    public void PackInt64_ShouldFallbackAndReturnCorrectValue_GivenNonPowerOfTwoLength_UsingSpan()
+    {
+        const long expected = 0b00000000_00000000_00000000_00000000_00000000_00000000_00000001_01010011;
+        Span<bool> span = stackalloc bool[10] {true, true, false, false, true, false, true, false, true, false};
+
+        long actual = span.PackInt64();
+
+        Assert.AreEqual(expected, actual);
+    }
+
     private enum EnumByte : byte
     {
         A,
diff --git a/X10D/src/Core/SpanExtensions.cs b/X10D/src/Core/SpanExtensions.cs
index 991b510..1ea3aaa 100644
--- a/X10D/src/Core/SpanExtensions.cs
+++ b/X10D/src/Core/SpanExtensions.cs
@@ -471,6 +471,8 @@ public static class SpanExtensions
         }
     }
 
+    // dotcover disable
+    //NOSONAR
     [Pure]
     [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
     internal static int PackInt32Internal_AdvSimd(this ReadOnlySpan<bool> source)
@@ -496,6 +498,8 @@ public static class SpanExtensions
             }
         }
     }
+    //NOSONAR
+    // dotcover enable
 
     [Pure]
     [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]