TestSuite.TUnit.AutoFixture

A streamlined, xUnit-compatible AutoFixture integration for TUnit - the modern .NET testing framework.

Features

• xUnit-Compatible Naming - Use [AutoData] and [InlineAutoData] just like in xUnit.AutoFixture
• Seamless Migration - Drop-in replacement for teams migrating from xUnit to TUnit
• Frozen Parameters - Full support for [Frozen] attribute with 5 matching strategies
• NSubstitute Integration - Auto-mocking with [AutoNSubstituteData]
• Immutable Collections - Automatic support for ImmutableArray, ImmutableList, ImmutableDictionary, and more (.NET 5.0+)
• AutoRegister - Automatic discovery and registration of customizations marked with [AutoRegister]
• FixtureFactory - Centralized factory for creating configured IFixture instances
• Custom Generators - Built-in generators for CancellationToken and DateOnly (.NET 6+)
• Comprehensive Tests - 81 passing tests demonstrating all features

Package

Package	Description	NuGet
TestSuite.TUnit.AutoFixture	Complete library with auto-generating test data and NSubstitute auto-mocking

All features in one package - No need to install separate packages for NSubstitute support!

Latest Release

Version 1.0.0 - Initial Stable Release (2026-01-21)

What's New in 1.0.0

• ✅ [AutoData] attribute for automatic test data generation
• ✅ [InlineAutoData] for combining explicit and auto-generated parameters
• ✅ [Frozen] attribute with 5 matching strategies (ExactType, ImplementedInterfaces, DirectBaseType, BaseType, MemberOfFamily)
• ✅ NSubstitute integration with [AutoNSubstituteData] and [InlineAutoNSubstituteData]
• ✅ xUnit-compatible naming - seamless migration from xUnit.AutoFixture
• ✅ Zero warnings - strict StyleCop and SonarAnalyzer compliance
• ✅ 48 passing tests - comprehensive test coverage with FluentAssertions
• ✅ Multi-platform CI/CD - automated testing on Ubuntu, Windows, and macOS
• ✅ .NET 10.0 support

Download

# Single package with all features included
dotnet add package TestSuite.TUnit.AutoFixture --version 1.0.1

📦 View on NuGet 📝 Full Release Notes 🏷️ GitHub Release

Latest Release

Version 1.0.0 - Initial Stable Release (2026-01-21)

What's New in 1.0.0

• ✅ [AutoData] attribute for automatic test data generation
• ✅ [InlineAutoData] for combining explicit and auto-generated parameters
• ✅ [Frozen] attribute with 5 matching strategies (ExactType, ImplementedInterfaces, DirectBaseType, BaseType, MemberOfFamily)
• ✅ NSubstitute integration with [AutoNSubstituteData] and [InlineAutoNSubstituteData]
• ✅ xUnit-compatible naming - seamless migration from xUnit.AutoFixture
• ✅ Zero warnings - strict StyleCop and SonarAnalyzer compliance
• ✅ 48 passing tests - comprehensive test coverage with FluentAssertions
• ✅ Multi-platform CI/CD - automated testing on Ubuntu, Windows, and macOS
• ✅ .NET 10.0 support

Quick Start

Installation

# Single package with all features (AutoFixture + NSubstitute)
dotnet add package TestSuite.TUnit.AutoFixture

Basic Usage

using TestSuite.TUnit.AutoFixture;
using TUnit.Core;

public class MyTests
{
    [Test]
    [AutoData]
    public void Test_WithAutoGeneratedData(string text, int number, Person person)
    {
        // All parameters are automatically generated by AutoFixture
        text.Should().NotBeNull();
        number.Should().NotBe(0);
        person.Should().NotBeNull();
    }

    [Test]
    [InlineAutoData("explicit value", 42)]
    public void Test_CombiningExplicitAndAutoData(
        string explicitText,
        int explicitNumber,
        Person autoPerson)
    {
        // First two parameters use explicit values
        // Third parameter is auto-generated
        explicitText.Should().Be("explicit value");
        explicitNumber.Should().Be(42);
        autoPerson.Should().NotBeNull();
    }

    [Test]
    [AutoData]
    public void Test_FrozenParameters(
        [Frozen] IService service,
        Consumer consumer)
    {
        // The same IService instance is injected into Consumer
        consumer.Service.Should().BeSameAs(service);
    }
}

With NSubstitute

using TestSuite.TUnit.AutoFixture;
using TUnit.Core;
using NSubstitute;

public class MyMockTests
{
    [Test]
    [AutoNSubstituteData]
    public void Test_WithAutoMocking(
        [Frozen] IRepository repository,
        Service sut)
    {
        // IRepository is automatically mocked
        repository.GetData().Returns("test data");

        var result = sut.ProcessData();

        result.Should().Be("test data");
        repository.Received(1).GetData();
    }
}

Using FixtureFactory Directly

You can use the FixtureFactory to create configured IFixture instances directly in your code:

using AutoFixture;
using TestSuite.TUnit.AutoFixture;

public class MyTests
{
    [Test]
    public void Test_DirectFixtureUsage()
    {
        // Create a configured fixture instance
        var fixture = FixtureFactory.Create();

        // Generate test data
        var person = fixture.Create<Person>();
        var numbers = fixture.CreateMany<int>(5);

        // All AutoRegister customizations are automatically applied
        person.Should().NotBeNull();
        numbers.Should().HaveCount(5);
    }
}

For NSubstitute-enabled fixtures:

using AutoFixture;
using TestSuite.TUnit.AutoFixture;

public class MyTests
{
    [Test]
    public void Test_DirectNSubstituteFixtureUsage()
    {
        // Create a fixture with NSubstitute auto-mocking
        var fixture = FixtureFactory.CreateWithNSubstitute();

        // Generate mocked interfaces and configured objects
        var service = fixture.Create<IService>();
        var consumer = fixture.Freeze<Consumer>();

        service.GetData().Returns("test");
        consumer.GetServiceData().Should().Be("test");
    }
}

The FixtureFactory provides:

• ✅ Centralized Configuration - All customizations in one place
• ✅ AutoRegister Support - Automatically applies [AutoRegister] marked customizations
• ✅ Immutable Collections - Built-in support for ImmutableArray, ImmutableList, etc. (.NET 5.0+)
• ✅ Consistent Behavior - Same configuration across all test attributes

Documentation

• TestSuite.TUnit.AutoFixture Documentation - Complete library usage guide
• AutoRegister Feature - Automatic customization discovery
• FixtureFactory Feature - Centralized fixture configuration
• Generators Feature - Built-in generators for CancellationToken and DateOnly
• Immutable Collections Feature - Immutable collection support (.NET 5.0+)
• Release Notes - Version history and changes

Why TestSuite.TUnit.AutoFixture?

xUnit Compatibility

If you're migrating from xUnit, you can use the exact same attribute names:

xUnit.AutoFixture	TestSuite.TUnit.AutoFixture	Status
[AutoData]	[AutoData]	✅ Identical
[InlineAutoData]	[InlineAutoData]	✅ Identical
[Frozen]	[Frozen]	✅ Identical
Matching enum	Matching enum	✅ Identical

No need to learn new attribute names or refactor your tests!

Simpler Architecture

Aspect	Official AutoFixture.TUnit	TestSuite.TUnit.AutoFixture
Core Classes	20+ internal classes	6-8 core classes
Primary Attribute	AutoDataSourceAttribute	AutoDataAttribute
Inline Attribute	AutoArgumentsAttribute	InlineAutoDataAttribute
Learning Curve	Steeper	Gentler
Extensibility	Multiple extension points	Focused, essential points

Feature Parity

All core AutoFixture features are supported:

• ✅ Auto-generation of primitives, complex types, collections, enums
• ✅ Frozen parameters with 5 matching strategies (ExactType, ImplementedInterfaces, DirectBaseType, BaseType, MemberOfFamily)
• ✅ Inline data combining explicit and auto-generated values
• ✅ NSubstitute auto-mocking integration
• ✅ Customization attributes
• ✅ Complex dependency graphs

Migration Guide

From xUnit.AutoFixture

// Before (xUnit)
using AutoFixture.Xunit2;
using Xunit;

public class MyTests
{
    [Theory]
    [AutoData]
    public void Test(string param) { }
}

// After (TUnit)
using TestSuite.TUnit.AutoFixture;
using TUnit.Core;

public class MyTests
{
    [Test]  // Changed from [Theory]
    [AutoData]
    public void Test(string param) { }
}

The only change needed is:

1. Replace [Theory] with [Test]
2. Update using statements

All [AutoData], [InlineAutoData], and [Frozen] attributes work identically!

From Official AutoFixture.TUnit

// Before (Official AutoFixture.TUnit)
using AutoFixture.TUnit;

[Test]
[AutoDataSource]  // Different name
public void Test(string param) { }

// After (TestSuite.TUnit.AutoFixture)
using TestSuite.TUnit.AutoFixture;

[Test]
[AutoData]  // xUnit-compatible name
public void Test(string param) { }

Examples

See the test project for comprehensive examples:

• BasicAutoDataTests.cs - Primitives, complex types, collections
• FrozenDependencyTests.cs - All 5 matching strategies
• InlineAutoDataTests.cs - Hybrid explicit/auto data
• AutoNSubstituteTests.cs - Auto-mocking scenarios
• ImmutableCollectionTests.cs - Immutable collection support (.NET 5.0+)
• AutoRegisterTests.cs - Custom customization auto-registration
• FixtureFactoryTests.cs - Direct FixtureFactory usage
• NSubstituteFixtureFactoryTests.cs - NSubstitute FixtureFactory usage

Requirements

• .NET 10.0 or later
• TUnit 1.10.0 or later
• AutoFixture 4.18.1 or later

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Building from Source

git clone https://github.com/kimlundjohansen/TUnit.AutoFixture.git
cd TUnit.AutoFixture
dotnet restore
dotnet build
dotnet test

All tests must pass with zero warnings before submitting a PR.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• AutoFixture - The excellent fixture library
• TUnit - Modern .NET testing framework
• Official AutoFixture.TUnit - Inspiration and reference implementation

Related Projects

• Official AutoFixture.TUnit - Official AutoFixture organization implementation
• AutoFixture.Xunit2 - xUnit integration
• AutoFixture.NUnit3 - NUnit integration

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Note: This is an independent implementation focused on xUnit compatibility and simplicity. For the official AutoFixture organization implementation, see AutoFixture.TUnit.