VSTest removes dependency on Newtonsoft.Json

The VSTest platform and Microsoft.NET.Test.SDK NuGet package no longer depend on Newtonsoft.Json. On .NET, System.Text.Json is used instead. On .NET Framework, JSONite is used.

Version introduced

.NET 11 Preview 4

Previous behavior

Previously, Microsoft.NET.Test.SDK brought a transitive dependency on Newtonsoft.Json into test projects. Newtonsoft.Json was available for compilation and at runtime without an explicit package reference. Projects that used Newtonsoft.Json types without declaring a direct dependency on the package compiled and ran successfully.

Additionally, VSTest's internal communication utilities exposed Newtonsoft.Json types (such as Newtonsoft.Json.Linq.JToken) in its public API.

New behavior

Starting in .NET 11, Newtonsoft.Json is no longer a transitive dependency of Microsoft.NET.Test.SDK. Projects that used Newtonsoft.Json types without a direct package reference fail to compile. Projects that excluded Newtonsoft.Json runtime assets and relied on the copy shipped with VSTest now fail at runtime with:

FileNotFoundException: Could not load 'Newtonsoft.Json'

Test extensions (such as data collectors or test adapters) that depended on Newtonsoft.Json being provided by VSTest also fail with:

Data collector 'SampleDataCollector' threw an exception during type loading, construction, or initialization:
System.IO.FileNotFoundException: Could not load file or assembly 'Newtonsoft.Json,
Version=13.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed'.

The Newtonsoft.Json-based types in Microsoft.VisualStudio.TestPlatform.CommunicationUtilities have been removed from the public API.

Type of breaking change

This change can affect source compatibility and binary compatibility.

Reason for change

To align the VSTest platform's dependencies with the .NET SDK and the broader .NET ecosystem, Newtonsoft.Json was removed as a dependency. To minimize unintended side effects on the code under test, the number of assemblies that VSTest adds to the test output folder is reduced. Test projects can bring exactly the dependencies they need at the versions they require.

Recommended action

In all cases, the fix is to add an explicit Newtonsoft.Json package reference to any project that uses it:

<PackageReference Include="Newtonsoft.Json" Version="..." />

Test projects that fail to compile

If your test project uses Newtonsoft.Json types (for example, JsonConvert, JToken, or JObject) without a direct package reference, add a PackageReference to Newtonsoft.Json in your test project file.

Tests that fail with FileNotFoundException at runtime

If your project has a PackageReference for Newtonsoft.Json with <ExcludeAssets>runtime</ExcludeAssets> and previously relied on the copy shipped with VSTest, remove the ExcludeAssets restriction or add a separate direct reference:

<!-- Before: excluded runtime assets, relying on VSTest to provide the DLL -->
<PackageReference Include="Newtonsoft.Json" Version="13.0.3">
  <ExcludeAssets>runtime</ExcludeAssets>
</PackageReference>

<!-- After: include runtime assets -->
<PackageReference Include="Newtonsoft.Json" Version="13.0.3" />

Test extensions that fail with FileNotFoundException

If you maintain or use a test extension (data collector or test adapter) that depended on Newtonsoft.Json being provided by VSTest, add Newtonsoft.Json as a direct dependency to the extension's project.

Affected APIs

The following Newtonsoft.Json-based APIs were removed from Microsoft.VisualStudio.TestPlatform.CommunicationUtilities:

• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Message.Payload property (type Newtonsoft.Json.Linq.JToken?)
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Serialization.DefaultTestPlatformContractResolver
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Serialization.TestCaseConverter
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Serialization.TestObjectConverter
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Serialization.TestPlatformContractResolver<T>
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Serialization.TestResultConverter
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.Serialization.TestRunStatisticsConverter
• Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.VersionedMessage