diff --git a/src/log4net.Tests/Appender/FileAppenderTest.cs b/src/log4net.Tests/Appender/FileAppenderTest.cs
new file mode 100644
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+++ b/src/log4net.Tests/Appender/FileAppenderTest.cs
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+#region Apache License
+
+//
+// Licensed to the Apache Software Foundation (ASF) under one or more 
+// contributor license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership. 
+// The ASF licenses this file to you under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with 
+// the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#endregion
+
+using System.Xml;
+using System;
+using log4net.Appender;
+using NUnit.Framework;
+using log4net.Repository;
+using log4net.Config;
+using log4net.Util;
+
+namespace log4net.Tests.Appender;
+
+/// <summary>
+/// Used for internal unit testing the <see cref="FileAppender"/> class.
+/// </summary>
+[TestFixture]
+public sealed class FileAppenderTest
+{
+  /// <summary>
+  /// Shuts down any loggers in the hierarchy, along with all appenders
+  /// </summary>
+  private static void Reset()
+  {
+    // Regular users should not use the clear method lightly!
+    LogManager.GetRepository().ResetConfiguration();
+    LogManager.GetRepository().Shutdown();
+    ((Repository.Hierarchy.Hierarchy)LogManager.GetRepository()).Clear();
+  }
+
+  /// <summary>
+  /// Any initialization that happens before each test can
+  /// go here
+  /// </summary>
+  [SetUp]
+  public void SetUp() => Reset();
+
+  /// <summary>
+  /// Any steps that happen after each test go here
+  /// </summary>
+  [TearDown]
+  public void TearDown() => Reset();
+
+  /// <summary>
+  /// Verifies that the <see cref="FileAppender.File"/> property accepts a <see cref="PatternString"/>
+  /// </summary>
+  [Test]
+  public void FilenameWithPatternStringTest()
+  {
+    LogLog.LogReceived += LogReceived;
+    try
+    {
+      XmlDocument log4netConfig = new();
+      log4netConfig.LoadXml("""
+  <log4net>
+    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
+      <layout type="log4net.Layout.PatternLayout">
+        <conversionPattern value="%date{ABSOLUTE} [%logger] %level - %message%newline%exception"/>
+      </layout>
+    </appender>
+    <appender name="GeneralFileAppender" type="log4net.Appender.FileAppender">
+      <file type="log4net.Util.PatternString" value="Logs\file_%property{LogName}_%date{yyyyMMddHHmmss}.Log"/>
+      <appendToFile value="true"/>
+      <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
+      <layout type="log4net.Layout.PatternLayout">
+        <conversionPattern value="%date{ABSOLUTE} [%logger] %level - %message%newline%exception"/>
+      </layout>
+    </appender>
+    <root>
+      <level value="INFO"/>
+      <appender-ref ref="GeneralFileAppender"/>
+    </root>
+  </log4net>
+""");
+      ILoggerRepository rep = LogManager.CreateRepository(Guid.NewGuid().ToString());
+      XmlConfigurator.Configure(rep, log4netConfig["log4net"]!);
+      ILog log = LogManager.GetLogger(rep.Name, "GeneralFileAppender");
+      log.Info("Message");
+    }
+    finally
+    {
+      LogLog.LogReceived += LogReceived;
+    }
+
+    static void LogReceived(object? source, LogReceivedEventArgs e) => Assert.Fail(e.LogLog.Message);
+  }
+}
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