xunit.v3 Migration

Migrate .NET test projects from xUnit.net v2 to xUnit.net v3. The outcome is a solution where all test projects reference

xunit.v3.*

packages, compiles cleanly, and all tests pass with the same results as before migration.

When to Use

• Upgrading test projects from

  xunit

  (v2) packages to

  xunit.v3

• Resolving compilation errors after updating xunit package references to v3

When Not to Use

• Migrating between test frameworks (e.g., MSTest or NUnit to xUnit.net) — different effort entirely
• Migrating from VSTest to Microsoft.Testing.Platform — use

  migrate-vstest-to-mtp

• The projects already reference

  xunit.v3

  — migration is done

Inputs

Input	Required	Description
Test project or solution	Yes	The .NET project or solution containing xUnit.net v2 test projects

Workflow

Commit strategy: Commit after each major step so the migration is reviewable and bisectable. Separate project file changes from code changes.

Step 1: Identify xUnit.net projects

Search for test projects referencing xUnit.net v2 packages:

• xunit

• xunit.abstractions

• xunit.assert

• xunit.core

• xunit.extensibility.core

• xunit.extensibility.execution

• xunit.runner.visualstudio

Make sure to check the package references in project files, MSBuild props and targets files, like

Directory.Build.props

,

Directory.Build.targets

, and

Directory.Packages.props

.

Step 2: Verify compatibility

1. Verify target framework compatibility: xUnit.net v3 requires .NET 8+ or .NET Framework 4.7.2+. For test library projects, .NET Standard 2.0 is also supported.
2. If any of the test projects have non-compatible target frameworks, STOP here and DON'T do anything. Only tell the user to upgrade the target framework first before migrating xUnit.net.
3. Verify project compatibility: xUnit.net v3 only supports SDK-style projects. If any test projects are non-SDK-style, STOP here and DON'T do anything. Only tell the user to migrate to SDK-style projects first before migrating xUnit.net.

Step 3: Establish a baseline

Run

dotnet test

to establish a baseline of test pass/fail counts. When running

dotnet test

, ensure that:

• You run

  dotnet test

  without any additional arguments (i.e., don't pass

  --no-restore

  or

  --no-build

  ).
• Ensure you redirect the command output to a file and read the output from that file.

Step 4: Update package references

1. Update any

   PackageReference

   or

   PackageVersion

   items for the new package names, based on the following mapping:

   • xunit

     →

     xunit.v3

   • xunit.abstractions

     → Remove entirely

   • xunit.assert

     →

     xunit.v3.assert

   • xunit.core

     →

     xunit.v3.core

   • xunit.extensibility.core

     and

     xunit.extensibility.execution

     →

     xunit.v3.extensibility.core

     (if both are referenced in a project consolidate to only a single entry as the two packages are merged)

2. Update all

   xunit.v3.*

   packages to the latest correct version available on NuGet. Also update

   xunit.runner.visualstudio

   to the latest version.

Step 5: Set

OutputType

to

Exe

In each test project (excluding test library projects), set

OutputType

to

Exe

in the project file:

<PropertyGroup>
  <OutputType>Exe</OutputType>
</PropertyGroup>

Depending on the solution in hand, there might be a centralized place where this can be added. For example:

• If all test projects share (or can share) a common

  Directory.Build.props

  , add the

  <OutputType>Exe</OutputType>

  property there. Note that the OutputType should not be added to

  Directory.Build.targets

  .
• If all test projects share a name pattern (e.g.,

  *.Tests.csproj

  ), add a conditional property group in

  Directory.Build.props

  that applies only to those projects, like

  <OutputType Condition="$(MSBuildProjectName.EndsWith('.Tests'))">Exe</OutputType>

  . Adjust the condition as needed to target only test projects.
• Otherwise, add the

  <OutputType>Exe</OutputType>

  property to each test project file individually.

Step 6: Remove

Xunit.Abstractions

usings

Find any

using Xunit.Abstractions;

directives in C# files and remove them completely.

Step 7: Address

async void

breaking change

In xUnit.net v3,

async void

test methods are no longer supported and will fail to compile. Search for any test methods declared with

async void

and change them to

async Task

. Test methods can be identified via the

[Fact]

or

[Theory]

attributes or other test attributes.

Step 8: Address breaking change of attributes

In xUnit.net v3, some attributes were updated so that they accept a

System.Type

instead of two strings (fully qualified type name and assembly name). These attributes are:

• CollectionBehaviorAttribute

• TestCaseOrdererAttribute

• TestCollectionOrdererAttribute

• TestFrameworkAttribute

For example,

[assembly: CollectionBehavior("MyNamespace.MyCollectionFactory", "MyAssembly")]

must be converted to

[assembly: CollectionBehavior(typeof(MyNamespace.MyCollectionFactory))]

.

Step 9: Inheriting from FactAttribute or TheoryAttribute

Identify if there are any custom attributes that inherit from

FactAttribute

or

TheoryAttribute

. These custom user-defined attributes must now provide source information. For example, if the attribute looked like this:

internal sealed class MyFactAttribute : FactAttribute
{
    public MyFactAttribute()
    {
    }
}

it must be changed to this:

internal sealed class MyFactAttribute : FactAttribute
{
    public MyFactAttribute(
        [CallerFilePath] string? sourceFilePath = null,
        [CallerLineNumber] int sourceLineNumber = -1
    ) : base(sourceFilePath, sourceLineNumber)
    {
    }
}

Step 10: Inheriting from BeforeAfterTestAttribute

Identify if there are any custom attributes that inherit from

BeforeAfterTestAttribute

. These custom user-defined attributes must update their method signatures. Previously, they would have

Before

/

After

overrides that look like this:

    public override void Before(MethodInfo methodUnderTest)
    {
        // Possibly some custom logic here
        base.Before(methodUnderTest);
        // Possibly some custom logic here
    }

    public override void After(MethodInfo methodUnderTest)
    {
        // Possibly some custom logic here
        base.After(methodUnderTest);
        // Possibly some custom logic here
    }

it must be changed to this:

    public override void Before(MethodInfo methodUnderTest, IXunitTest test)
    {
        // Possibly some custom logic here
        base.Before(methodUnderTest, test);
        // Possibly some custom logic here
    }

    public override void After(MethodInfo methodUnderTest, IXunitTest test)
    {
        // Possibly some custom logic here
        base.After(methodUnderTest, test);
        // Possibly some custom logic here
    }

Step 11: Address new xUnit analyzer warnings

xunit.v3 introduced new analyzer warnings. You should attempt to address them.

One of the most notable warnings is xUnit1051: Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken. Identify the calls to such methods, if any, and pass the cancellation token.

Step 12: Test platform selection

You should keep the same test platform that was used with xunit 2.

Note that xunit 2 is always VSTest except if the user used YTest.MTP.XUnit2.

• If user had a reference to YTest.MTP.XUnit2:
  • Remove the reference to YTest.MTP.XUnit2 completely.
  • Add

    <UseMicrosoftTestingPlatformRunner>true</UseMicrosoftTestingPlatformRunner>

    to Directory.Build.props under an unconditional PropertyGroup.
• If user didn't have a reference to YTest.MTP.XUnit2:
  • Add

    <IsTestingPlatformApplication>false</IsTestingPlatformApplication>

    to Directory.Build.props under an unconditional PropertyGroup.

Step 13: Migrate

Xunit.SkippableFact

If there are any package references to

Xunit.SkippableFact

, remove all these package references entirely.

Then, follow these steps to eliminate usages of APIs coming from the removed package reference:

• Update any

  SkippableFact

  attribute to the regular

  Fact

  attribute.
• Update any

  SkippableTheory

  attribute to the regular

  Theory

  attribute.
• Change

  Skip.If

  method calls to

  Assert.SkipWhen

  .
• Change

  Skip.IfNot

  method calls to

  Assert.SkipUnless

  .

Step 14: Update

Xunit.Combinatorial

NuGet package

Find package references of

Xunit.Combinatorial

and update them from 1.x to the latest 2.x version available.

Step 15: Update

Xunit.StaFact

NuGet package

Find package references of

Xunit.StaFact

and update them from 1.x to the latest 3.x version available.

Step 16: Build the solution

Now, build the solution to identify any remaining compilation errors that might not have been addressed by previous instructions. Fix any straightforward errors that show up, and keep iterating and fixing more.

You can also look into https://xunit.net/docs/getting-started/v3/migration-extensibility and https://xunit.net/docs/getting-started/v3/migration to help with the remaining compilation errors.

You can fix as much as you can, and it's okay if not everything is fixed. Just tell the user that there are remaining errors that need to be manually addressed.