diff --git a/Structural/DesignPatterns.Decorator/CompressionDecorator.cs b/Structural/DesignPatterns.Decorator/CompressionDecorator.cs
index 9780e2b..ca11ab7 100644
--- a/Structural/DesignPatterns.Decorator/CompressionDecorator.cs
+++ b/Structural/DesignPatterns.Decorator/CompressionDecorator.cs
@@ -1,3 +1,5 @@
+using System.IO.Compression;
+
 namespace DesignPatterns.Decorator;
 
 internal class CompressionDecorator : UploaderDecorator
@@ -9,10 +11,9 @@ public CompressionDecorator(IFileUploader uploader)
 
     public override async Task Upload(string name, Stream stream)
     {
-        // TODO: add compression logic here.
-        Console.WriteLine($"{nameof(CompressionDecorator)}.{nameof(Upload)}: started compressing a file...");
-        await Task.Delay(1000);
-        Console.WriteLine($"{nameof(CompressionDecorator)}.{nameof(Upload)}: completed compressing a file.");
-        await base.Upload(name, stream);
+        using MemoryStream compressedStream = new MemoryStream();
+        await using var compressor = new GZipStream(compressedStream, CompressionMode.Compress);
+        await stream.CopyToAsync(compressor);
+        await base.Upload(name, compressor.BaseStream);
     }
 }
diff --git a/Structural/DesignPatterns.Decorator/DesignPatterns.Decorator.csproj b/Structural/DesignPatterns.Decorator/DesignPatterns.Decorator.csproj
index 2f4fc77..844e1c1 100644
--- a/Structural/DesignPatterns.Decorator/DesignPatterns.Decorator.csproj
+++ b/Structural/DesignPatterns.Decorator/DesignPatterns.Decorator.csproj
@@ -7,4 +7,10 @@
         <Nullable>enable</Nullable>
     </PropertyGroup>
 
+    <ItemGroup>
+        <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
+            <_Parameter1>$(MSBuildProjectName).UnitTests</_Parameter1>
+        </AssemblyAttribute>
+    </ItemGroup>
+
 </Project>