diff --git a/readme.md b/readme.md
index 9d556a1..e2c705c 100644
--- a/readme.md
+++ b/readme.md
@@ -37,6 +37,116 @@ npm run build:dev
 
 > Create a development build of the extension.
 
+## Testing
+
+A C# unit-test project can be used to test the extension in a self-owned Azure
+DevOps organisation.
+
+```csharp
+[TestClass]
+public class UnitTests
+{
+    public TestContext? TestContext { get; set; }
+
+    [TestCleanup]
+    public void TestCleanup()
+    { 
+        this.TestContext!.AddResultFile("./attachments/test.svg");
+        this.TestContext!.AddResultFile("./attachments/test.mp4");
+        this.TestContext!.AddResultFile("./attachments/test.html");
+        this.TestContext!.AddResultFile("./attachments/test.pdf");
+        this.TestContext!.AddResultFile("./attachments/test.yaml");
+        this.TestContext!.AddResultFile("./attachments/test.txt");
+        this.TestContext!.AddResultFile("./attachments/fake.pdf");
+    }
+
+    [TestMethod]
+    public void TestMethod_Pass()
+    {
+        Assert.AreEqual("abc", "abc");
+    }
+
+    [TestMethod]
+    public void TestMethod_Fail()
+    {
+        Assert.AreEqual("abc", "123");
+    }
+}
+```
+
+> Example unit-test class that uploads the release pipeline attachments.
+
+```yaml
+steps:
+
+- task: VisualStudioTestPlatformInstaller@1
+  displayName: 'Install Visual Studio Test Platform'
+  inputs:
+    versionSelector: latestStable
+
+- task: NuGetToolInstaller@1
+  displayName: 'Use NuGet'
+  inputs:
+    checkLatest: true
+
+- powershell: |
+   New-Item -ItemType Directory -Force -Path $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments
+
+   Invoke-WebRequest "https://filesamples.com/samples/image/svg/sample_640%C3%97426.svg" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\test.svg
+   Invoke-WebRequest "https://filesamples.com/samples/video/mp4/sample_960x540.mp4" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\test.mp4
+   Invoke-WebRequest "https://filesamples.com/samples/code/html/sample1.html" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\test.html
+   Invoke-WebRequest "https://filesamples.com/samples/document/pdf/sample3.pdf" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\test.pdf
+   Invoke-WebRequest "https://filesamples.com/samples/code/yaml/invoice.yaml" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\test.yaml
+   Invoke-WebRequest "https://filesamples.com/samples/code/yaml/invoice.yaml" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\test.txt
+
+   Invoke-WebRequest "https://filesamples.com/samples/code/html/sample1.html" -OutFile $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments\fake.pdf
+  displayName: Setup
+
+- task: NuGetCommand@2
+  displayName: 'NuGet Restore'
+  inputs:
+    restoreSolution: '$(System.DefaultWorkingDirectory)/_ado-attachment-previewer-tests/test-project/test-project.sln'
+
+- task: MSBuild@1
+  displayName: 'Build Solution'
+  inputs:
+    solution: '$(System.DefaultWorkingDirectory)/_ado-attachment-previewer-tests/test-project/test-project.sln'
+    msbuildArchitecture: x64
+
+- powershell: |
+   Move-Item $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\attachments $(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project\bin\Debug\net6.0\attachments
+  displayName: 'Move Attachments'
+
+- task: VSTest@2
+  displayName: 'Run Visual Studio Tests Without Reruns'
+  inputs:
+    testAssemblyVer2: '**\test-project.dll'
+    searchFolder: '$(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project'
+    vsTestVersion: toolsInstaller
+  continueOnError: true
+
+- task: VSTest@2
+  displayName: 'Run Visual Studio Tests With Reruns'
+  inputs:
+    testAssemblyVer2: '**\test-project.dll'
+    searchFolder: '$(System.DefaultWorkingDirectory)\_ado-attachment-previewer-tests\test-project'
+    vsTestVersion: toolsInstaller
+    rerunFailedTests: true
+    rerunType: basedOnTestFailureCount
+  continueOnError: true
+
+- task: PublishTestResults@2
+  displayName: Publish
+  inputs:
+    testResultsFormat: NUnit
+    testResultsFiles: testresult.xml
+    searchFolder: '$(Agent.TempDirectory)/TestResults'
+  continueOnError: true
+```
+
+> Exported YAML of steps for release pipeline. Requires the git repository that
+> includes the C# unit-test project as an artifact.
+
 ## Maintainers
 
   - [@shawnfunke](https://github.com/shawnfunke)