diff --git a/src/Neo.CLI/CLI/MainService.Network.cs b/src/Neo.CLI/CLI/MainService.Network.cs
index c579b8323e..49a056640e 100644
--- a/src/Neo.CLI/CLI/MainService.Network.cs
+++ b/src/Neo.CLI/CLI/MainService.Network.cs
@@ -11,6 +11,7 @@
 
 using Akka.Actor;
 using Neo.ConsoleService;
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Json;
 using Neo.Network.P2P;
diff --git a/src/Neo.Extensions/AssemblyExtensions.cs b/src/Neo.Extensions/AssemblyExtensions.cs
new file mode 100644
index 0000000000..4f9368c98b
--- /dev/null
+++ b/src/Neo.Extensions/AssemblyExtensions.cs
@@ -0,0 +1,23 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// AssemblyExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using System.Reflection;
+
+namespace Neo.Extensions
+{
+    public static class AssemblyExtensions
+    {
+        public static string GetVersion(this Assembly assembly)
+        {
+            return assembly.GetName().Version!.ToString(3);
+        }
+    }
+}
diff --git a/src/Neo.Extensions/Collections/HashSetExtensions.cs b/src/Neo.Extensions/Collections/HashSetExtensions.cs
new file mode 100644
index 0000000000..9cf3f13b23
--- /dev/null
+++ b/src/Neo.Extensions/Collections/HashSetExtensions.cs
@@ -0,0 +1,42 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// HashSetExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using System.Collections.Generic;
+
+namespace Neo.Extensions
+{
+    public static class HashSetExtensions
+    {
+        public static void Remove<T>(this HashSet<T> set, ISet<T> other)
+        {
+            if (set.Count > other.Count)
+            {
+                set.ExceptWith(other);
+            }
+            else
+            {
+                set.RemoveWhere(u => other.Contains(u));
+            }
+        }
+
+        public static void Remove<T, V>(this HashSet<T> set, IReadOnlyDictionary<T, V> other)
+        {
+            if (set.Count > other.Count)
+            {
+                set.ExceptWith(other.Keys);
+            }
+            else
+            {
+                set.RemoveWhere(u => other.ContainsKey(u));
+            }
+        }
+    }
+}
diff --git a/src/Neo.Extensions/DateTimeExtensions.cs b/src/Neo.Extensions/DateTimeExtensions.cs
new file mode 100644
index 0000000000..130d09e78d
--- /dev/null
+++ b/src/Neo.Extensions/DateTimeExtensions.cs
@@ -0,0 +1,38 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// DateTimeExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using System;
+
+namespace Neo.Extensions
+{
+    public static class DateTimeExtensions
+    {
+        /// <summary>
+        /// Converts a <see cref="DateTime"/> to timestamp.
+        /// </summary>
+        /// <param name="time">The <see cref="DateTime"/> to convert.</param>
+        /// <returns>The converted timestamp.</returns>
+        public static uint ToTimestamp(this DateTime time)
+        {
+            return (uint)new DateTimeOffset(time.ToUniversalTime()).ToUnixTimeSeconds();
+        }
+
+        /// <summary>
+        /// Converts a <see cref="DateTime"/> to timestamp in milliseconds.
+        /// </summary>
+        /// <param name="time">The <see cref="DateTime"/> to convert.</param>
+        /// <returns>The converted timestamp.</returns>
+        public static ulong ToTimestampMS(this DateTime time)
+        {
+            return (ulong)new DateTimeOffset(time.ToUniversalTime()).ToUnixTimeMilliseconds();
+        }
+    }
+}
diff --git a/src/Neo.Extensions/Net/IpAddressExtensions.cs b/src/Neo.Extensions/Net/IpAddressExtensions.cs
new file mode 100644
index 0000000000..adafee142f
--- /dev/null
+++ b/src/Neo.Extensions/Net/IpAddressExtensions.cs
@@ -0,0 +1,40 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// IpAddressExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using System.Net;
+
+namespace Neo.Extensions
+{
+    public static class IpAddressExtensions
+    {
+        /// <summary>
+        /// Checks if address is IPv4 Mapped to IPv6 format, if so, Map to IPv4.
+        /// Otherwise, return current address.
+        /// </summary>
+        public static IPAddress UnMap(this IPAddress address)
+        {
+            if (address.IsIPv4MappedToIPv6)
+                address = address.MapToIPv4();
+            return address;
+        }
+
+        /// <summary>
+        /// Checks if IPEndPoint is IPv4 Mapped to IPv6 format, if so, unmap to IPv4.
+        /// Otherwise, return current endpoint.
+        /// </summary>
+        public static IPEndPoint UnMap(this IPEndPoint endPoint)
+        {
+            if (!endPoint.Address.IsIPv4MappedToIPv6)
+                return endPoint;
+            return new IPEndPoint(endPoint.Address.UnMap(), endPoint.Port);
+        }
+    }
+}
diff --git a/src/Neo.Extensions/RandomExtensions.cs b/src/Neo.Extensions/RandomExtensions.cs
new file mode 100644
index 0000000000..72bcac289f
--- /dev/null
+++ b/src/Neo.Extensions/RandomExtensions.cs
@@ -0,0 +1,34 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// RandomExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using System;
+using System.Numerics;
+
+namespace Neo.Extensions
+{
+    public static class RandomExtensions
+    {
+        public static BigInteger NextBigInteger(this Random rand, int sizeInBits)
+        {
+            if (sizeInBits < 0)
+                throw new ArgumentException("sizeInBits must be non-negative");
+            if (sizeInBits == 0)
+                return 0;
+            Span<byte> b = stackalloc byte[sizeInBits / 8 + 1];
+            rand.NextBytes(b);
+            if (sizeInBits % 8 == 0)
+                b[^1] = 0;
+            else
+                b[^1] &= (byte)((1 << sizeInBits % 8) - 1);
+            return new BigInteger(b);
+        }
+    }
+}
diff --git a/src/Neo.Extensions/StringExtensions.cs b/src/Neo.Extensions/StringExtensions.cs
new file mode 100644
index 0000000000..8d851bf905
--- /dev/null
+++ b/src/Neo.Extensions/StringExtensions.cs
@@ -0,0 +1,36 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// StringExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using System;
+using System.Globalization;
+
+namespace Neo.Extensions
+{
+    public static class StringExtensions
+    {
+        /// <summary>
+        /// Converts a hex <see cref="string"/> to byte array.
+        /// </summary>
+        /// <param name="value">The hex <see cref="string"/> to convert.</param>
+        /// <returns>The converted byte array.</returns>
+        public static byte[] HexToBytes(this string value)
+        {
+            if (value == null || value.Length == 0)
+                return [];
+            if (value.Length % 2 == 1)
+                throw new FormatException();
+            var result = new byte[value.Length / 2];
+            for (var i = 0; i < result.Length; i++)
+                result[i] = byte.Parse(value.Substring(i * 2, 2), NumberStyles.AllowHexSpecifier);
+            return result;
+        }
+    }
+}
diff --git a/src/Neo.GUI/GUI/CreateMultiSigContractDialog.cs b/src/Neo.GUI/GUI/CreateMultiSigContractDialog.cs
index 5dd10f858f..d28696f138 100644
--- a/src/Neo.GUI/GUI/CreateMultiSigContractDialog.cs
+++ b/src/Neo.GUI/GUI/CreateMultiSigContractDialog.cs
@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using Neo.SmartContract;
 using Neo.Wallets;
 using System;
diff --git a/src/Neo.GUI/GUI/ImportCustomContractDialog.cs b/src/Neo.GUI/GUI/ImportCustomContractDialog.cs
index b8df534699..8faa23d593 100644
--- a/src/Neo.GUI/GUI/ImportCustomContractDialog.cs
+++ b/src/Neo.GUI/GUI/ImportCustomContractDialog.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.SmartContract;
 using Neo.Wallets;
 using System;
diff --git a/src/Neo.GUI/GUI/ParametersEditor.cs b/src/Neo.GUI/GUI/ParametersEditor.cs
index 19eac82c31..f5156d6bfb 100644
--- a/src/Neo.GUI/GUI/ParametersEditor.cs
+++ b/src/Neo.GUI/GUI/ParametersEditor.cs
@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using Neo.SmartContract;
 using System;
 using System.Collections.Generic;
diff --git a/src/Neo.IO/Caching/HashSetCache.cs b/src/Neo.IO/Caching/HashSetCache.cs
index 577893e924..6e39f5fd8b 100644
--- a/src/Neo.IO/Caching/HashSetCache.cs
+++ b/src/Neo.IO/Caching/HashSetCache.cs
@@ -15,7 +15,7 @@
 
 namespace Neo.IO.Caching
 {
-    class HashSetCache<T> : IReadOnlyCollection<T> where T : IEquatable<T>
+    internal class HashSetCache<T> : IReadOnlyCollection<T> where T : IEquatable<T>
     {
         /// <summary>
         /// Sets where the Hashes are stored
diff --git a/src/Neo.IO/Neo.IO.csproj b/src/Neo.IO/Neo.IO.csproj
index a51ec1110a..deb98b053b 100644
--- a/src/Neo.IO/Neo.IO.csproj
+++ b/src/Neo.IO/Neo.IO.csproj
@@ -12,7 +12,8 @@
   <ItemGroup>
     <InternalsVisibleTo Include="Neo" />
     <InternalsVisibleTo Include="Neo.UnitTests" />
-    <InternalsVisibleTo Include="$(AssemblyName).Tests" />
+    <InternalsVisibleTo Include="Neo.Extensions" />
+    <InternalsVisibleTo Include="Neo.Extensions.Tests" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/Neo/Cryptography/ECC/ECCurve.cs b/src/Neo/Cryptography/ECC/ECCurve.cs
index def1ee0cb1..805507a08e 100644
--- a/src/Neo/Cryptography/ECC/ECCurve.cs
+++ b/src/Neo/Cryptography/ECC/ECCurve.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using System.Globalization;
 using System.Numerics;
 
diff --git a/src/Neo/Extensions/HashSetExtensions.cs b/src/Neo/Extensions/HashSetExtensions.cs
new file mode 100644
index 0000000000..fb4648b16e
--- /dev/null
+++ b/src/Neo/Extensions/HashSetExtensions.cs
@@ -0,0 +1,36 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// HashSetExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using Neo.IO.Caching;
+using System;
+using System.Collections.Generic;
+
+namespace Neo.Extensions
+{
+    /// <summary>
+    /// A helper class that provides common functions.
+    /// </summary>
+    public static class HashSetExtensions
+    {
+        internal static void Remove<T>(this HashSet<T> set, HashSetCache<T> other)
+            where T : IEquatable<T>
+        {
+            if (set.Count > other.Count)
+            {
+                set.ExceptWith(other);
+            }
+            else
+            {
+                set.RemoveWhere(u => other.Contains(u));
+            }
+        }
+    }
+}
diff --git a/src/Neo/Helper.cs b/src/Neo/Helper.cs
deleted file mode 100644
index 4458d04f42..0000000000
--- a/src/Neo/Helper.cs
+++ /dev/null
@@ -1,148 +0,0 @@
-// Copyright (C) 2015-2024 The Neo Project.
-//
-// Helper.cs file belongs to the neo project and is free
-// software distributed under the MIT software license, see the
-// accompanying file LICENSE in the main directory of the
-// repository or http://www.opensource.org/licenses/mit-license.php
-// for more details.
-//
-// Redistribution and use in source and binary forms with or without
-// modifications are permitted.
-
-using Neo.IO.Caching;
-using System;
-using System.Collections.Generic;
-using System.Globalization;
-using System.Linq;
-using System.Net;
-using System.Numerics;
-using System.Reflection;
-
-namespace Neo
-{
-    /// <summary>
-    /// A helper class that provides common functions.
-    /// </summary>
-    public static class Helper
-    {
-        private static readonly DateTime unixEpoch = new(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
-
-        internal static void Remove<T>(this HashSet<T> set, ISet<T> other)
-        {
-            if (set.Count > other.Count)
-            {
-                set.ExceptWith(other);
-            }
-            else
-            {
-                set.RemoveWhere(u => other.Contains(u));
-            }
-        }
-
-        internal static void Remove<T>(this HashSet<T> set, HashSetCache<T> other)
-            where T : IEquatable<T>
-        {
-            if (set.Count > other.Count)
-            {
-                set.ExceptWith(other);
-            }
-            else
-            {
-                set.RemoveWhere(u => other.Contains(u));
-            }
-        }
-
-        internal static void Remove<T, V>(this HashSet<T> set, IReadOnlyDictionary<T, V> other)
-        {
-            if (set.Count > other.Count)
-            {
-                set.ExceptWith(other.Keys);
-            }
-            else
-            {
-                set.RemoveWhere(u => other.ContainsKey(u));
-            }
-        }
-
-        internal static string GetVersion(this Assembly assembly)
-        {
-            CustomAttributeData attribute = assembly.CustomAttributes.FirstOrDefault(p => p.AttributeType == typeof(AssemblyInformationalVersionAttribute));
-            if (attribute == null) return assembly.GetName().Version.ToString(3);
-            return (string)attribute.ConstructorArguments[0].Value;
-        }
-
-        /// <summary>
-        /// Converts a hex <see cref="string"/> to byte array.
-        /// </summary>
-        /// <param name="value">The hex <see cref="string"/> to convert.</param>
-        /// <returns>The converted byte array.</returns>
-        public static byte[] HexToBytes(this string value)
-        {
-            if (value == null || value.Length == 0)
-                return Array.Empty<byte>();
-            if (value.Length % 2 == 1)
-                throw new FormatException();
-            byte[] result = new byte[value.Length / 2];
-            for (int i = 0; i < result.Length; i++)
-                result[i] = byte.Parse(value.Substring(i * 2, 2), NumberStyles.AllowHexSpecifier);
-            return result;
-        }
-
-        internal static BigInteger NextBigInteger(this Random rand, int sizeInBits)
-        {
-            if (sizeInBits < 0)
-                throw new ArgumentException("sizeInBits must be non-negative");
-            if (sizeInBits == 0)
-                return 0;
-            Span<byte> b = stackalloc byte[sizeInBits / 8 + 1];
-            rand.NextBytes(b);
-            if (sizeInBits % 8 == 0)
-                b[^1] = 0;
-            else
-                b[^1] &= (byte)((1 << sizeInBits % 8) - 1);
-            return new BigInteger(b);
-        }
-
-        /// <summary>
-        /// Converts a <see cref="DateTime"/> to timestamp.
-        /// </summary>
-        /// <param name="time">The <see cref="DateTime"/> to convert.</param>
-        /// <returns>The converted timestamp.</returns>
-        public static uint ToTimestamp(this DateTime time)
-        {
-            return (uint)(time.ToUniversalTime() - unixEpoch).TotalSeconds;
-        }
-
-        /// <summary>
-        /// Converts a <see cref="DateTime"/> to timestamp in milliseconds.
-        /// </summary>
-        /// <param name="time">The <see cref="DateTime"/> to convert.</param>
-        /// <returns>The converted timestamp.</returns>
-        public static ulong ToTimestampMS(this DateTime time)
-        {
-            return (ulong)(time.ToUniversalTime() - unixEpoch).TotalMilliseconds;
-        }
-
-        /// <summary>
-        /// Checks if address is IPv4 Mapped to IPv6 format, if so, Map to IPv4.
-        /// Otherwise, return current address.
-        /// </summary>
-        internal static IPAddress Unmap(this IPAddress address)
-        {
-            if (address.IsIPv4MappedToIPv6)
-                address = address.MapToIPv4();
-            return address;
-        }
-
-        /// <summary>
-        /// Checks if IPEndPoint is IPv4 Mapped to IPv6 format, if so, unmap to IPv4.
-        /// Otherwise, return current endpoint.
-        /// </summary>
-        internal static IPEndPoint Unmap(this IPEndPoint endPoint)
-        {
-            if (!endPoint.Address.IsIPv4MappedToIPv6)
-                return endPoint;
-            return new IPEndPoint(endPoint.Address.Unmap(), endPoint.Port);
-        }
-    }
-}
diff --git a/src/Neo/NeoSystem.cs b/src/Neo/NeoSystem.cs
index 3121432db5..99be387712 100644
--- a/src/Neo/NeoSystem.cs
+++ b/src/Neo/NeoSystem.cs
@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Akka.Actor;
+using Neo.Extensions;
 using Neo.IO.Caching;
 using Neo.Ledger;
 using Neo.Network.P2P;
diff --git a/src/Neo/Network/P2P/Payloads/NetworkAddressWithTime.cs b/src/Neo/Network/P2P/Payloads/NetworkAddressWithTime.cs
index d3cfd15f66..0b7e0acc37 100644
--- a/src/Neo/Network/P2P/Payloads/NetworkAddressWithTime.cs
+++ b/src/Neo/Network/P2P/Payloads/NetworkAddressWithTime.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Network.P2P.Capabilities;
 using System;
@@ -68,7 +69,7 @@ void ISerializable.Deserialize(ref MemoryReader reader)
 
             // Address
             ReadOnlyMemory<byte> data = reader.ReadMemory(16);
-            Address = new IPAddress(data.Span).Unmap();
+            Address = new IPAddress(data.Span).UnMap();
 
             // Capabilities
             Capabilities = new NodeCapability[reader.ReadVarInt(VersionPayload.MaxCapabilities)];
diff --git a/src/Neo/Network/P2P/Payloads/PingPayload.cs b/src/Neo/Network/P2P/Payloads/PingPayload.cs
index f6296a7713..6ac3d2d94e 100644
--- a/src/Neo/Network/P2P/Payloads/PingPayload.cs
+++ b/src/Neo/Network/P2P/Payloads/PingPayload.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.IO;
 using System;
 using System.IO;
diff --git a/src/Neo/Network/P2P/Payloads/VersionPayload.cs b/src/Neo/Network/P2P/Payloads/VersionPayload.cs
index 8cec6278e7..f8fe74a856 100644
--- a/src/Neo/Network/P2P/Payloads/VersionPayload.cs
+++ b/src/Neo/Network/P2P/Payloads/VersionPayload.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Network.P2P.Capabilities;
 using System;
diff --git a/src/Neo/Network/P2P/Peer.cs b/src/Neo/Network/P2P/Peer.cs
index 767d747b1d..074c5cf3ba 100644
--- a/src/Neo/Network/P2P/Peer.cs
+++ b/src/Neo/Network/P2P/Peer.cs
@@ -11,6 +11,7 @@
 
 using Akka.Actor;
 using Akka.IO;
+using Neo.Extensions;
 using Neo.IO;
 using System;
 using System.Buffers.Binary;
@@ -138,7 +139,7 @@ protected virtual int ConnectingMax
 
         static Peer()
         {
-            localAddresses.UnionWith(NetworkInterface.GetAllNetworkInterfaces().SelectMany(p => p.GetIPProperties().UnicastAddresses).Select(p => p.Address.Unmap()));
+            localAddresses.UnionWith(NetworkInterface.GetAllNetworkInterfaces().SelectMany(p => p.GetIPProperties().UnicastAddresses).Select(p => p.Address.UnMap()));
         }
 
         /// <summary>
@@ -163,7 +164,7 @@ protected void AddPeers(IEnumerable<IPEndPoint> peers)
         /// <param name="isTrusted">Indicates whether the remote node is trusted. A trusted node will always be connected.</param>
         protected void ConnectToPeer(IPEndPoint endPoint, bool isTrusted = false)
         {
-            endPoint = endPoint.Unmap();
+            endPoint = endPoint.UnMap();
             // If the address is the same, the ListenerTcpPort should be different, otherwise, return
             if (endPoint.Port == ListenerTcpPort && localAddresses.Contains(endPoint.Address)) return;
 
@@ -210,7 +211,7 @@ protected override void OnReceive(object message)
                     ConnectToPeer(connect.EndPoint, connect.IsTrusted);
                     break;
                 case Tcp.Connected connected:
-                    OnTcpConnected(((IPEndPoint)connected.RemoteAddress).Unmap(), ((IPEndPoint)connected.LocalAddress).Unmap());
+                    OnTcpConnected(((IPEndPoint)connected.RemoteAddress).UnMap(), ((IPEndPoint)connected.LocalAddress).UnMap());
                     break;
                 case Tcp.Bound _:
                     tcp_listener = Sender;
@@ -302,7 +303,7 @@ private void OnTcpCommandFailed(Tcp.Command cmd)
             switch (cmd)
             {
                 case Tcp.Connect connect:
-                    ImmutableInterlocked.Update(ref ConnectingPeers, p => p.Remove(((IPEndPoint)connect.RemoteAddress).Unmap()));
+                    ImmutableInterlocked.Update(ref ConnectingPeers, p => p.Remove(((IPEndPoint)connect.RemoteAddress).UnMap()));
                     break;
             }
         }
diff --git a/src/Neo/Network/P2P/TaskManager.cs b/src/Neo/Network/P2P/TaskManager.cs
index e9c12e58a4..c5708df923 100644
--- a/src/Neo/Network/P2P/TaskManager.cs
+++ b/src/Neo/Network/P2P/TaskManager.cs
@@ -12,6 +12,7 @@
 using Akka.Actor;
 using Akka.Configuration;
 using Akka.IO;
+using Neo.Extensions;
 using Neo.IO.Actors;
 using Neo.IO.Caching;
 using Neo.Ledger;
diff --git a/src/Plugins/DBFTPlugin/Consensus/ConsensusContext.MakePayload.cs b/src/Plugins/DBFTPlugin/Consensus/ConsensusContext.MakePayload.cs
index f68f004c3c..a1e9b28bc4 100644
--- a/src/Plugins/DBFTPlugin/Consensus/ConsensusContext.MakePayload.cs
+++ b/src/Plugins/DBFTPlugin/Consensus/ConsensusContext.MakePayload.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.Ledger;
 using Neo.Network.P2P.Payloads;
 using Neo.Plugins.DBFTPlugin.Messages;
diff --git a/src/Plugins/DBFTPlugin/Consensus/ConsensusService.OnMessage.cs b/src/Plugins/DBFTPlugin/Consensus/ConsensusService.OnMessage.cs
index 3c6ab8e243..b00fdd9393 100644
--- a/src/Plugins/DBFTPlugin/Consensus/ConsensusService.OnMessage.cs
+++ b/src/Plugins/DBFTPlugin/Consensus/ConsensusService.OnMessage.cs
@@ -11,6 +11,7 @@
 
 using Akka.Actor;
 using Neo.Cryptography;
+using Neo.Extensions;
 using Neo.Ledger;
 using Neo.Network.P2P;
 using Neo.Network.P2P.Payloads;
diff --git a/src/Plugins/RpcClient/RpcClient.cs b/src/Plugins/RpcClient/RpcClient.cs
index 27b0023ec0..7866c7e40f 100644
--- a/src/Plugins/RpcClient/RpcClient.cs
+++ b/src/Plugins/RpcClient/RpcClient.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Json;
 using Neo.Network.P2P.Payloads;
diff --git a/src/Plugins/RpcClient/Utility.cs b/src/Plugins/RpcClient/Utility.cs
index 659942f8f8..37331eec1b 100644
--- a/src/Plugins/RpcClient/Utility.cs
+++ b/src/Plugins/RpcClient/Utility.cs
@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using Neo.Json;
 using Neo.Network.P2P.Payloads;
 using Neo.Network.P2P.Payloads.Conditions;
diff --git a/src/Plugins/TokensTracker/Trackers/NEP-17/Nep17Tracker.cs b/src/Plugins/TokensTracker/Trackers/NEP-17/Nep17Tracker.cs
index d4698cba1e..71bfceb49d 100644
--- a/src/Plugins/TokensTracker/Trackers/NEP-17/Nep17Tracker.cs
+++ b/src/Plugins/TokensTracker/Trackers/NEP-17/Nep17Tracker.cs
@@ -9,6 +9,7 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+using Neo.Extensions;
 using Neo.Json;
 using Neo.Ledger;
 using Neo.Network.P2P.Payloads;
diff --git a/tests/Neo.Cryptography.MPTTrie.Tests/Cryptography/MPTTrie/UT_Trie.cs b/tests/Neo.Cryptography.MPTTrie.Tests/Cryptography/MPTTrie/UT_Trie.cs
index 05592d366b..2e53456545 100644
--- a/tests/Neo.Cryptography.MPTTrie.Tests/Cryptography/MPTTrie/UT_Trie.cs
+++ b/tests/Neo.Cryptography.MPTTrie.Tests/Cryptography/MPTTrie/UT_Trie.cs
@@ -17,7 +17,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using static Neo.Helper;
 
 namespace Neo.Cryptography.MPTTrie.Tests
 {
diff --git a/tests/Neo.Extensions.Tests/Collections/UT_HashSetExtensions.cs b/tests/Neo.Extensions.Tests/Collections/UT_HashSetExtensions.cs
new file mode 100644
index 0000000000..cb475a7e5c
--- /dev/null
+++ b/tests/Neo.Extensions.Tests/Collections/UT_HashSetExtensions.cs
@@ -0,0 +1,75 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// UT_HashSetExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using Neo.IO.Caching;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Neo.Extensions.Tests.Collections
+{
+    [TestClass]
+    public class UT_HashSetExtensions
+    {
+        [TestMethod]
+        public void TestRemoveHashsetDictionary()
+        {
+            var a = new HashSet<int>
+            {
+                1,
+                2,
+                3
+            };
+
+            var b = new Dictionary<int, object>
+            {
+                [2] = null
+            };
+
+            a.Remove(b);
+
+            CollectionAssert.AreEqual(new int[] { 1, 3 }, a.ToArray());
+
+            b[4] = null;
+            b[5] = null;
+            b[1] = null;
+            a.Remove(b);
+
+            CollectionAssert.AreEqual(new int[] { 3 }, a.ToArray());
+        }
+
+        [TestMethod]
+        public void TestRemoveHashsetSet()
+        {
+            var a = new HashSet<int>
+            {
+                1,
+                2,
+                3
+            };
+
+            var b = new SortedSet<int>()
+            {
+                2
+            };
+
+            a.Remove(b);
+
+            CollectionAssert.AreEqual(new int[] { 1, 3 }, a.ToArray());
+
+            b.Add(4);
+            b.Add(5);
+            b.Add(1);
+            a.Remove(b);
+
+            CollectionAssert.AreEqual(new int[] { 3 }, a.ToArray());
+        }
+    }
+}
diff --git a/tests/Neo.Extensions.Tests/Neo.Extensions.Tests.csproj b/tests/Neo.Extensions.Tests/Neo.Extensions.Tests.csproj
index 3c13dd0953..03809a4fe3 100644
--- a/tests/Neo.Extensions.Tests/Neo.Extensions.Tests.csproj
+++ b/tests/Neo.Extensions.Tests/Neo.Extensions.Tests.csproj
@@ -12,7 +12,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\..\src\Neo.Extensions\Neo.Extensions.csproj" />
     <ProjectReference Include="..\..\src\Neo\Neo.csproj" />
   </ItemGroup>
 
diff --git a/tests/Neo.Extensions.Tests/Net/UT_IpAddressExtensions.cs b/tests/Neo.Extensions.Tests/Net/UT_IpAddressExtensions.cs
new file mode 100644
index 0000000000..bbf26c5cb7
--- /dev/null
+++ b/tests/Neo.Extensions.Tests/Net/UT_IpAddressExtensions.cs
@@ -0,0 +1,43 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// UT_IpAddressExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using FluentAssertions;
+using Neo.Extensions;
+using System.Net;
+
+namespace Neo.Extensions.Tests.Net
+{
+    [TestClass]
+    public class UT_IpAddressExtensions
+    {
+        [TestMethod]
+        public void TestUnmapForIPAddress()
+        {
+            var addr = new IPAddress(new byte[] { 127, 0, 0, 1 });
+            addr.UnMap().Should().Be(addr);
+
+            var addr2 = addr.MapToIPv6();
+            addr2.UnMap().Should().Be(addr);
+        }
+
+        [TestMethod]
+        public void TestUnmapForIPEndPoin()
+        {
+            var addr = new IPAddress(new byte[] { 127, 0, 0, 1 });
+            var endPoint = new IPEndPoint(addr, 8888);
+            endPoint.UnMap().Should().Be(endPoint);
+
+            var addr2 = addr.MapToIPv6();
+            var endPoint2 = new IPEndPoint(addr2, 8888);
+            endPoint2.UnMap().Should().Be(endPoint);
+        }
+    }
+}
diff --git a/tests/Neo.Extensions.Tests/UT_AssemblyExtensions.cs b/tests/Neo.Extensions.Tests/UT_AssemblyExtensions.cs
new file mode 100644
index 0000000000..43f66f95da
--- /dev/null
+++ b/tests/Neo.Extensions.Tests/UT_AssemblyExtensions.cs
@@ -0,0 +1,33 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// UT_AssemblyExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using FluentAssertions;
+using System;
+using System.Linq;
+
+namespace Neo.Extensions.Tests
+{
+    [TestClass]
+    public class UT_AssemblyExtensions
+    {
+        [TestMethod]
+        public void TestGetVersion()
+        {
+            // assembly without version
+
+            var asm = AppDomain.CurrentDomain.GetAssemblies()
+                .Where(u => u.FullName == "Anonymously Hosted DynamicMethods Assembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")
+                .FirstOrDefault();
+            string version = asm?.GetVersion() ?? "";
+            version.Should().Be("0.0.0");
+        }
+    }
+}
diff --git a/tests/Neo.Extensions.Tests/UT_DateTimeExtensions.cs b/tests/Neo.Extensions.Tests/UT_DateTimeExtensions.cs
new file mode 100644
index 0000000000..43414a8f81
--- /dev/null
+++ b/tests/Neo.Extensions.Tests/UT_DateTimeExtensions.cs
@@ -0,0 +1,42 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// UT_DateTimeExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using FluentAssertions;
+using System;
+
+namespace Neo.Extensions.Tests
+{
+    [TestClass]
+    public class UT_DateTimeExtensions
+    {
+        private static readonly DateTime unixEpoch = new(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+
+        [TestMethod]
+        public void TestToTimestamp()
+        {
+            var time = DateTime.Now;
+            var expected = (uint)(time.ToUniversalTime() - unixEpoch).TotalSeconds;
+            var actual = time.ToTimestamp();
+
+            actual.Should().Be(expected);
+        }
+
+        [TestMethod]
+        public void TestToTimestampMS()
+        {
+            var time = DateTime.Now;
+            var expected = (ulong)(time.ToUniversalTime() - unixEpoch).TotalMilliseconds;
+            var actual = time.ToTimestampMS();
+
+            actual.Should().Be(expected);
+        }
+    }
+}
diff --git a/tests/Neo.Extensions.Tests/UT_RandomExtensions.cs b/tests/Neo.Extensions.Tests/UT_RandomExtensions.cs
new file mode 100644
index 0000000000..fb7c6a8cf7
--- /dev/null
+++ b/tests/Neo.Extensions.Tests/UT_RandomExtensions.cs
@@ -0,0 +1,32 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// UT_RandomExtensions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using FluentAssertions;
+using System;
+
+namespace Neo.Extensions.Tests
+{
+    [TestClass]
+    public class UT_RandomExtensions
+    {
+        [TestMethod]
+        public void TestNextBigIntegerForRandom()
+        {
+            Random ran = new();
+            Action action1 = () => ran.NextBigInteger(-1);
+            action1.Should().Throw<ArgumentException>();
+
+            ran.NextBigInteger(0).Should().Be(0);
+            ran.NextBigInteger(8).Should().NotBeNull();
+            ran.NextBigInteger(9).Should().NotBeNull();
+        }
+    }
+}
diff --git a/tests/Neo.Extensions.Tests/UT_StringExtensions.cs b/tests/Neo.Extensions.Tests/UT_StringExtensions.cs
new file mode 100644
index 0000000000..9954f24765
--- /dev/null
+++ b/tests/Neo.Extensions.Tests/UT_StringExtensions.cs
@@ -0,0 +1,39 @@
+// Copyright (C) 2015-2024 The Neo Project.
+//
+// UT_StringExtensdions.cs file belongs to the neo project and is free
+// software distributed under the MIT software license, see the
+// accompanying file LICENSE in the main directory of the
+// repository or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using FluentAssertions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Neo.Extensions.Tests
+{
+    [TestClass]
+    public class UT_StringExtensions
+    {
+        [TestMethod]
+        public void TestHexToBytes()
+        {
+            string nullStr = null;
+            _ = nullStr.HexToBytes().ToHexString().Should().Be(Array.Empty<byte>().ToHexString());
+            string emptyStr = "";
+            emptyStr.HexToBytes().ToHexString().Should().Be(Array.Empty<byte>().ToHexString());
+            string str1 = "hab";
+            Action action = () => str1.HexToBytes();
+            action.Should().Throw<FormatException>();
+            string str2 = "0102";
+            byte[] bytes = str2.HexToBytes();
+            bytes.ToHexString().Should().Be(new byte[] { 0x01, 0x02 }.ToHexString());
+        }
+    }
+}
diff --git a/tests/Neo.Network.RPC.Tests/UT_ContractClient.cs b/tests/Neo.Network.RPC.Tests/UT_ContractClient.cs
index c3cf226a3e..6ac90dafc5 100644
--- a/tests/Neo.Network.RPC.Tests/UT_ContractClient.cs
+++ b/tests/Neo.Network.RPC.Tests/UT_ContractClient.cs
@@ -11,6 +11,7 @@
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
+using Neo.Extensions;
 using Neo.SmartContract;
 using Neo.SmartContract.Manifest;
 using Neo.SmartContract.Native;
diff --git a/tests/Neo.Network.RPC.Tests/UT_Nep17API.cs b/tests/Neo.Network.RPC.Tests/UT_Nep17API.cs
index 863d424405..ef156a5b05 100644
--- a/tests/Neo.Network.RPC.Tests/UT_Nep17API.cs
+++ b/tests/Neo.Network.RPC.Tests/UT_Nep17API.cs
@@ -11,6 +11,7 @@
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
+using Neo.Extensions;
 using Neo.Json;
 using Neo.SmartContract;
 using Neo.SmartContract.Native;
@@ -19,7 +20,6 @@
 using System.Linq;
 using System.Numerics;
 using System.Threading.Tasks;
-using static Neo.Helper;
 
 namespace Neo.Network.RPC.Tests
 {
diff --git a/tests/Neo.UnitTests/Cryptography/ECC/UT_ECFieldElement.cs b/tests/Neo.UnitTests/Cryptography/ECC/UT_ECFieldElement.cs
index 3d4e4c56f2..0d1e20c37a 100644
--- a/tests/Neo.UnitTests/Cryptography/ECC/UT_ECFieldElement.cs
+++ b/tests/Neo.UnitTests/Cryptography/ECC/UT_ECFieldElement.cs
@@ -12,6 +12,7 @@
 using FluentAssertions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using System;
 using System.Globalization;
 using System.Numerics;
diff --git a/tests/Neo.UnitTests/Cryptography/ECC/UT_ECPoint.cs b/tests/Neo.UnitTests/Cryptography/ECC/UT_ECPoint.cs
index 4b0c7d484f..e5767acd37 100644
--- a/tests/Neo.UnitTests/Cryptography/ECC/UT_ECPoint.cs
+++ b/tests/Neo.UnitTests/Cryptography/ECC/UT_ECPoint.cs
@@ -12,6 +12,7 @@
 using FluentAssertions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using Neo.IO;
 using System;
 using System.IO;
diff --git a/tests/Neo.UnitTests/Cryptography/UT_Base58.cs b/tests/Neo.UnitTests/Cryptography/UT_Base58.cs
index e7cb467dfa..091513862c 100644
--- a/tests/Neo.UnitTests/Cryptography/UT_Base58.cs
+++ b/tests/Neo.UnitTests/Cryptography/UT_Base58.cs
@@ -12,6 +12,7 @@
 using FluentAssertions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography;
+using Neo.Extensions;
 using System;
 using System.Collections.Generic;
 
diff --git a/tests/Neo.UnitTests/Cryptography/UT_Crypto.cs b/tests/Neo.UnitTests/Cryptography/UT_Crypto.cs
index e311d6cafe..2f7de65b77 100644
--- a/tests/Neo.UnitTests/Cryptography/UT_Crypto.cs
+++ b/tests/Neo.UnitTests/Cryptography/UT_Crypto.cs
@@ -12,6 +12,7 @@
 using FluentAssertions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography;
+using Neo.Extensions;
 using Neo.Wallets;
 using System;
 using System.Security.Cryptography;
diff --git a/tests/Neo.UnitTests/IO/UT_MemoryReader.cs b/tests/Neo.UnitTests/IO/UT_MemoryReader.cs
index a045a0b688..25278b3e22 100644
--- a/tests/Neo.UnitTests/IO/UT_MemoryReader.cs
+++ b/tests/Neo.UnitTests/IO/UT_MemoryReader.cs
@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.Extensions;
 using Neo.IO;
 using System.IO;
 using System.Text;
diff --git a/tests/Neo.UnitTests/Ledger/UT_MemoryPool.cs b/tests/Neo.UnitTests/Ledger/UT_MemoryPool.cs
index 45cdee05c7..ca4e08341e 100644
--- a/tests/Neo.UnitTests/Ledger/UT_MemoryPool.cs
+++ b/tests/Neo.UnitTests/Ledger/UT_MemoryPool.cs
@@ -14,6 +14,7 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 using Neo.Cryptography;
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Ledger;
 using Neo.Network.P2P.Payloads;
diff --git a/tests/Neo.UnitTests/SmartContract/Manifest/UT_ContractManifest.cs b/tests/Neo.UnitTests/SmartContract/Manifest/UT_ContractManifest.cs
index 4e2e866281..fdbcf671b2 100644
--- a/tests/Neo.UnitTests/SmartContract/Manifest/UT_ContractManifest.cs
+++ b/tests/Neo.UnitTests/SmartContract/Manifest/UT_ContractManifest.cs
@@ -11,6 +11,7 @@
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Json;
 using Neo.SmartContract;
diff --git a/tests/Neo.UnitTests/SmartContract/UT_SmartContractHelper.cs b/tests/Neo.UnitTests/SmartContract/UT_SmartContractHelper.cs
index 42308d91f2..d223c747f6 100644
--- a/tests/Neo.UnitTests/SmartContract/UT_SmartContractHelper.cs
+++ b/tests/Neo.UnitTests/SmartContract/UT_SmartContractHelper.cs
@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Network.P2P.Payloads;
 using Neo.Persistence;
diff --git a/tests/Neo.UnitTests/TestUtils.Block.cs b/tests/Neo.UnitTests/TestUtils.Block.cs
index bed85131e6..dd1ad77625 100644
--- a/tests/Neo.UnitTests/TestUtils.Block.cs
+++ b/tests/Neo.UnitTests/TestUtils.Block.cs
@@ -11,6 +11,7 @@
 
 using Akka.Util.Internal;
 using Neo.Cryptography;
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Network.P2P.Payloads;
 using Neo.Persistence;
diff --git a/tests/Neo.UnitTests/TestUtils.Transaction.cs b/tests/Neo.UnitTests/TestUtils.Transaction.cs
index f6d6ebd4b5..12e9b4ec0e 100644
--- a/tests/Neo.UnitTests/TestUtils.Transaction.cs
+++ b/tests/Neo.UnitTests/TestUtils.Transaction.cs
@@ -11,7 +11,7 @@
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Neo.Cryptography;
-using Neo.Cryptography.ECC;
+using Neo.Extensions;
 using Neo.IO;
 using Neo.Network.P2P.Payloads;
 using Neo.Persistence;
diff --git a/tests/Neo.UnitTests/UT_Helper.cs b/tests/Neo.UnitTests/UT_Helper.cs
index 413c9dcf31..6cf1605a24 100644
--- a/tests/Neo.UnitTests/UT_Helper.cs
+++ b/tests/Neo.UnitTests/UT_Helper.cs
@@ -51,75 +51,6 @@ public void ToScriptHash()
             res.Should().Be(UInt160.Parse("2d3b96ae1bcc5a585e075e3b81920210dec16302"));
         }
 
-        [TestMethod]
-        public void TestHexToBytes()
-        {
-            string nullStr = null;
-            _ = nullStr.HexToBytes().ToHexString().Should().Be(Array.Empty<byte>().ToHexString());
-            string emptyStr = "";
-            emptyStr.HexToBytes().ToHexString().Should().Be(Array.Empty<byte>().ToHexString());
-            string str1 = "hab";
-            Action action = () => str1.HexToBytes();
-            action.Should().Throw<FormatException>();
-            string str2 = "0102";
-            byte[] bytes = str2.HexToBytes();
-            bytes.ToHexString().Should().Be(new byte[] { 0x01, 0x02 }.ToHexString());
-        }
-
-        [TestMethod]
-        public void TestRemoveHashsetDictionary()
-        {
-            var a = new HashSet<int>
-            {
-                1,
-                2,
-                3
-            };
-
-            var b = new Dictionary<int, object>
-            {
-                [2] = null
-            };
-
-            a.Remove(b);
-
-            CollectionAssert.AreEqual(new int[] { 1, 3 }, a.ToArray());
-
-            b[4] = null;
-            b[5] = null;
-            b[1] = null;
-            a.Remove(b);
-
-            CollectionAssert.AreEqual(new int[] { 3 }, a.ToArray());
-        }
-
-        [TestMethod]
-        public void TestRemoveHashsetSet()
-        {
-            var a = new HashSet<int>
-            {
-                1,
-                2,
-                3
-            };
-
-            var b = new SortedSet<int>()
-            {
-                2
-            };
-
-            a.Remove(b);
-
-            CollectionAssert.AreEqual(new int[] { 1, 3 }, a.ToArray());
-
-            b.Add(4);
-            b.Add(5);
-            b.Add(1);
-            a.Remove(b);
-
-            CollectionAssert.AreEqual(new int[] { 3 }, a.ToArray());
-        }
-
         [TestMethod]
         public void TestRemoveHashsetHashSetCache()
         {
@@ -146,51 +77,5 @@ public void TestRemoveHashsetHashSetCache()
 
             CollectionAssert.AreEqual(new int[] { 3 }, a.ToArray());
         }
-
-        [TestMethod]
-        public void TestGetVersion()
-        {
-            // assembly without version
-
-            var asm = AppDomain.CurrentDomain.GetAssemblies()
-                .Where(u => u.FullName == "Anonymously Hosted DynamicMethods Assembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null")
-                .FirstOrDefault();
-            string version = asm?.GetVersion() ?? "";
-            version.Should().Be("0.0.0");
-        }
-
-        [TestMethod]
-        public void TestNextBigIntegerForRandom()
-        {
-            Random ran = new();
-            Action action1 = () => ran.NextBigInteger(-1);
-            action1.Should().Throw<ArgumentException>();
-
-            ran.NextBigInteger(0).Should().Be(0);
-            ran.NextBigInteger(8).Should().NotBeNull();
-            ran.NextBigInteger(9).Should().NotBeNull();
-        }
-
-        [TestMethod]
-        public void TestUnmapForIPAddress()
-        {
-            var addr = new IPAddress(new byte[] { 127, 0, 0, 1 });
-            addr.Unmap().Should().Be(addr);
-
-            var addr2 = addr.MapToIPv6();
-            addr2.Unmap().Should().Be(addr);
-        }
-
-        [TestMethod]
-        public void TestUnmapForIPEndPoin()
-        {
-            var addr = new IPAddress(new byte[] { 127, 0, 0, 1 });
-            var endPoint = new IPEndPoint(addr, 8888);
-            endPoint.Unmap().Should().Be(endPoint);
-
-            var addr2 = addr.MapToIPv6();
-            var endPoint2 = new IPEndPoint(addr2, 8888);
-            endPoint2.Unmap().Should().Be(endPoint);
-        }
     }
 }
diff --git a/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Contract.cs b/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Contract.cs
index 37f816c240..bac6c0d4eb 100644
--- a/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Contract.cs
+++ b/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Contract.cs
@@ -11,6 +11,7 @@
 
 using FluentAssertions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.Extensions;
 using Neo.Json;
 using Neo.SmartContract;
 using Neo.Wallets.NEP6;
diff --git a/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Wallet.cs b/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Wallet.cs
index a914b235b7..3f3a61ca03 100644
--- a/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Wallet.cs
+++ b/tests/Neo.UnitTests/Wallets/NEP6/UT_NEP6Wallet.cs
@@ -11,6 +11,7 @@
 
 using FluentAssertions;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.Extensions;
 using Neo.Json;
 using Neo.Network.P2P.Payloads;
 using Neo.SmartContract;