# How to get XUnit v3 to work with Test Explorer in VS Code

I recently upgraded some xUnit v2 test projects to v3 because I needed two awesome features that v3 introduced:

*   [Assembly Fixtures](https://xunit.net/docs/shared-context#assembly-fixture): These allow a fixture instance to be shared between all tests in multiple classes, rather than between tests in a single class as `IClassFixture` had allowed up until v2.
    
*   Automatically serialization of test case objects in `TheoryData` classes. This means that this unbelievable clunk:
    
    ```csharp
     public class TestCase_ValidProduct : IXunitSerializable
     {
    	public required string TestCaseName { get; set; }
    	public required CreateProductArgs NewProduct { get; set; }
    
    	public void Deserialize(IXunitSerializationInfo info)
    	{
    		XUnitSerializationHelper.Deserialize(this, info);
    	}
    
    	public void Serialize(IXunitSerializationInfo info)
    	{
    		XUnitSerializationHelper.Serialize(this, info);
    	}
     }
    ```
    
    reduces to:
    
    ```csharp
    public class TestCase_ValidProduct : IXunitSerializable
    {
    	public required string TestCaseName { get; set; }
    	public required CreateProductArgs NewProduct { get; set; }
    }
    ```
    

The price of this upgrade was that Test Explorer in VS Code either couldn't discover tests, or would show them as "Skipped" and refuse to run them:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jdlxuh5knw18vvoa74sq.png align="center")

Exactly the same thing happens when I scaffold a new XUnit 3 project using `dotnet new xunit3`.

These problems seem to stem from the fact that xUnit v3 uses the new [Microsoft Test Platform (MTP)](https://learn.microsoft.com/en-us/dotnet/core/testing/microsoft-testing-platform-intro) which is a replacement for the older [VS Test](https://github.com/microsoft/vstest) platform, but C# Dev Kit extension in VS Code - which is [responsible for discovering tests in a C# test project](https://code.visualstudio.com/docs/csharp/testing) and providing these to the Test Explorer window - does not work properly with MTP (yet!).

It is worth mentioning that both VS Test and the newer MTP are *test execution platforms* - they are agnostic to the test harness used in test projects and works with any test harness e.g. MS Test, xUnit and NUnit.

I fixed the issues by making the test projects use the older VS Test platform instead that C# Dev Kit *does* work with.

These are the **steps that you can take** to make an xUnit v3 project - whether upgraded from v2 or newly scaffolded - work in Test Explorer in VS Code:

*   Delete `<PackageReference>` to `xunit.v3.mtp-v2` or just comment it out in the `.csproj` of your test project:
    
    ```xml
    <!--<PackageReference Include="xunit.v3.mtp-v2" Version="3.2.2" />-->
    ```
    
*   Then add the following references:
    
    ```bash
    dotnet add package xunit.v3.mtp-off
    dotnet add package Microsoft.NET.Test.Sdk
    dotnet add package xunit.runner.visualstudio
    ```
    
    `xunit.v3.mtp-off` is a version of xUnit v3 package that has [MTP support disabled](https://xunit.net/docs/getting-started/v3/microsoft-testing-platform#choosing-the-microsoft-testing-platform-version) and is a replacement for `xunit.v3.mtp-v2` that I deleted above.
    
    [`Microsoft.NET.Test.Sdk`](https://www.nuget.org/packages/microsoft.net.test.sdk/#readme-body-tab) provides targets and properties for building .NET test projects, regardless of the test harness - xUnit, NUnit, MS Test etc. - that they use. It is required for integrating the project with the VS Test platform.
    
    [`xunit.runner.visualstudio`](https://www.nuget.org/packages/xunit.runner.visualstudio) is the xUnit-specific adapter for VS Test
    

Then reload the window (bring up the Command Palette using shortcut key `Ctrl+Shift+P` or `F12`, then type **Reload Window** and press Enter), and press **Refresh Tests** button in **Test Explorer**:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9onecapgg3gogm0ttnhq.png align="center")

You should now be able to see and run your tests.

The slight caveat is that individual TheoryData tests cases in a `[Theory]` test do not appear as separate tests cases like they used in the Test Explorer with xUnit v2. But I am happy to sacrifice this granularity for being able to use the shiny new features in xUnit v3.