diff --git a/tests/Magick.NET.Tests/TestHelpers/TemporaryFile.cs b/tests/Magick.NET.Tests/TestHelpers/TemporaryFile.cs
index eab1538d26..94db448e69 100644
--- a/tests/Magick.NET.Tests/TestHelpers/TemporaryFile.cs
+++ b/tests/Magick.NET.Tests/TestHelpers/TemporaryFile.cs
@@ -6,7 +6,7 @@
 
 namespace Magick.NET.Tests;
 
-public class TemporaryFile : IDisposable
+public sealed class TemporaryFile : IDisposable
 {
     private readonly FileInfo _file;
 
@@ -39,7 +39,7 @@ public FileInfo File
     public void Dispose()
         => Cleanup.DeleteFile(_file);
 
-    private FileInfo CreateEmptyFile(string fileName)
+    private static FileInfo CreateEmptyFile(string fileName)
     {
         var file = new FileInfo(Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString() + fileName));
         file.Create().Dispose();
@@ -48,7 +48,7 @@ private FileInfo CreateEmptyFile(string fileName)
         return file;
     }
 
-    private FileInfo CreateFromFile(string fileName)
+    private static FileInfo CreateFromFile(string fileName)
     {
         var file = new FileInfo(Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString() + Path.GetFileName(fileName)));
         FileHelper.Copy(fileName, file.FullName);