Generated test class fails "required member must be set in object initializer"

[TheRumle]

Info

• IDE: JetBrains Rider 2025.2.4
• TUnit version: 1.3.0 and also recreated on 1.2.11

Recreation of the problem

I have a compositional hierarchy equivalent to this the following classes:

public sealed class MyTestGeneratorAttribute<T> : DataSourceGeneratorAttribute<T> where T : MyType, new() 
{
    protected override IEnumerable<Func<T>> GenerateDataSources(DataGeneratorMetadata dataGeneratorMetadata) => [() => new T()];
}

public class MyType;

public class ErrContext: IAsyncInitializer, IAsyncDisposable
{
    public ValueTask DisposeAsync() => ValueTask.CompletedTask;
    public Task InitializeAsync() => Task.CompletedTask;
}

public class ErrFixture<T> : IAsyncDisposable, IAsyncInitializer
{ 
    public required ErrContext Fixture { get; set; }
    public ValueTask DisposeAsync() => ValueTask.CompletedTask;
    public Task InitializeAsync() => Task.CompletedTask;
}

public class ErrTest
{
    [ClassDataSource<ErrFixture<MyType>>(Shared = SharedType.PerClass)]
    public required ErrFixture<MyType> Fixture { get; init; }
    
    public IEnumerable<Func<ErrContext>> TestExecutions => [() => Fixture.Fixture];
    
    [MethodDataSource("TestExecutions")]

    [Test]
    public async Task MyTest(ErrContext context)
    {
        await Assert.That(context.GetType()).IsNotAssignableTo<MyType>();
    }
    
    [MyTestGeneratorAttribute<MyType>]
    [Test]
    public async Task MyTest2(MyType t)
    {
        await Assert.That(t.GetType()).IsAssignableTo<MyType>();
    }
}

This generates the following file that has compile time error:

// <auto-generated/>
#pragma warning disable

#nullable enable
namespace TUnit.Generated;
internal sealed class MyNamespace_ErrTest_MyFailingTestIsHere__ErrContext_TestSource : global::TUnit.Core.Interfaces.SourceGenerator.ITestSource
{
    #if NET8_0_OR_GREATER
    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Field, Name = "<Fixture>k__BackingField")]
    private static extern ref global::MyNamespace.ErrFixture<global::MyNamespace.MyType> GetFixtureBackingField(global::MyNamespace.ErrTest instance);
    #endif
    public async global::System.Collections.Generic.IAsyncEnumerable<global::TUnit.Core.TestMetadata> GetTestsAsync(string testSessionId, [global::System.Runtime.CompilerServices.EnumeratorCancellation] global::System.Threading.CancellationToken cancellationToken = default)
    {
        var metadata = new global::TUnit.Core.TestMetadata<global::MyNamespace.ErrTest>
        {
            TestName = "MyFailingTestIsHere",
            TestClassType = typeof(global::MyNamespace.ErrTest),
            TestMethodName = "MyFailingTestIsHere",
            Dependencies = global::System.Array.Empty<global::TUnit.Core.TestDependency>(),
            AttributeFactory = static () =>
            [
                new global::TUnit.Core.TestAttribute(),
                new global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Design", "S3993")
{Justification = "TUnits' attributeusage must not and cannot be overwritten.",},
                new global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Maintainability", "S4144")
{Justification =             "This is a test class and method consuming code will not accidentally call wrong method due to similar signatures.",},
                new global::TUnit.Core.ParallelLimiterAttribute<global::Hoeyer.OpcUa.EndToEndTest.Configuration.ParallelLimit>(),
                new global::System.Reflection.AssemblyCompanyAttribute("Hoeyer.OpcUa.EndToEndTest"),
                new global::System.Reflection.AssemblyConfigurationAttribute("Debug"),
                new global::System.Reflection.AssemblyFileVersionAttribute("1.0.0.0"),
                new global::System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+6ce90c5365417e7937319199a18c15ee9dcf63c7"),
                new global::System.Reflection.AssemblyProductAttribute("Hoeyer.OpcUa.EndToEndTest"),
                new global::System.Reflection.AssemblyTitleAttribute("Hoeyer.OpcUa.EndToEndTest"),
                new global::System.Reflection.AssemblyVersionAttribute("1.0.0.0"),
                new global::System.Reflection.AssemblyMetadataAttribute("Microsoft.Testing.Platform.Application", "true")
            ],
            DataSources = new global::TUnit.Core.IDataSourceAttribute[]
            {
                new global::TUnit.Core.MethodDataSourceAttribute("TestExecutions")
                {
                    Factory = (dataGeneratorMetadata) =>
                    {
                        async global::System.Collections.Generic.IAsyncEnumerable<global::System.Func<global::System.Threading.Tasks.Task<object?[]?>>> Factory()
                        {
                            object? instance;
                            if (dataGeneratorMetadata.TestClassInstance != null)
                            {
                                instance = dataGeneratorMetadata.TestClassInstance;
                            }
                            else
                            {
                                instance = new global::MyNamespace.ErrTest();
                            }
                            var result = ((global::MyNamespace.ErrTest)instance).TestExecutions;
                            if (result is global::System.Collections.IEnumerable enumerable && !(result is string))
                            {
                                foreach (var item in enumerable)
                                {
                                    yield return () => global::System.Threading.Tasks.Task.FromResult(global::TUnit.Core.Helpers.DataSourceHelpers.ToObjectArray(item));
                                }
                            }
                            else
                            {
                                yield return () => global::System.Threading.Tasks.Task.FromResult(global::TUnit.Core.Helpers.DataSourceHelpers.ToObjectArray(result));
                            }
                        }
                        return Factory();
                    }
                },
            },
            ClassDataSources = global::System.Array.Empty<global::TUnit.Core.IDataSourceAttribute>(),
            PropertyDataSources = new global::TUnit.Core.PropertyDataSource[]
            {
                new global::TUnit.Core.PropertyDataSource
                {
                    PropertyName = "Fixture",
                    PropertyType = typeof(global::MyNamespace.ErrFixture<global::MyNamespace.MyType>),
                    DataSource = new global::TUnit.Core.ClassDataSourceAttribute<global::MyNamespace.ErrFixture<global::MyNamespace.MyType>>()
{Shared = global::TUnit.Core.SharedType.PerClass,},
                },
            },
            PropertyInjections = new global::TUnit.Core.PropertyInjectionData[]
            {
                new global::TUnit.Core.PropertyInjectionData
                {
                    PropertyName = "Fixture",
                    PropertyType = typeof(global::MyNamespace.ErrFixture<global::MyNamespace.MyType>),
                    #if NET8_0_OR_GREATER
                    Setter = (instance, value) => GetFixtureBackingField((global::MyNamespace.ErrTest)instance) = (global::MyNamespace.ErrFixture<global::MyNamespace.MyType>)value,
                    #else
                    Setter = (instance, value) => throw new global::System.NotSupportedException("Setting init-only properties requires .NET 8 or later"),
                    #endif
                    ValueFactory = () => throw new global::System.InvalidOperationException("ValueFactory should be provided by TestDataCombination"),
                    NestedPropertyInjections = global::System.Array.Empty<global::TUnit.Core.PropertyInjectionData>(),
                    NestedPropertyValueFactory = obj =>
                    {
                        return new global::System.Collections.Generic.Dictionary<string, object?>();
                    }
                },
            },
            InheritanceDepth = 0,
            FilePath = @"C:\\Users\\rasmus\\RiderProjects\\Hoeyer.Opcua\\Hoeyer.OpcUa.EndToEndTest\\ClientTests\\ErrTest.cs",
            LineNumber = 33,
            MethodMetadata = new global::TUnit.Core.MethodMetadata
            {
                Type = typeof(global::MyNamespace.ErrTest),
                TypeInfo = new global::TUnit.Core.ConcreteType(typeof(global::MyNamespace.ErrTest)),
                Name = "MyFailingTestIsHere",
                GenericTypeCount = 0,
                ReturnType = typeof(global::System.Threading.Tasks.Task),
                ReturnTypeInfo = new global::TUnit.Core.ConcreteType(typeof(global::System.Threading.Tasks.Task)),
                Parameters = new global::TUnit.Core.ParameterMetadata[]
                {
                    new global::TUnit.Core.ParameterMetadata(typeof(global::MyNamespace.ErrContext))
                    {
                        Name = "context",
                        TypeInfo = new global::TUnit.Core.ConcreteType(typeof(global::MyNamespace.ErrContext)),
                        IsNullable = false,
                        ReflectionInfo = typeof(global::MyNamespace.ErrTest).GetMethod("MyFailingTestIsHere", global::System.Reflection.BindingFlags.Public | global::System.Reflection.BindingFlags.NonPublic | global::System.Reflection.BindingFlags.Instance, null, new global::System.Type[] { typeof(global::MyNamespace.ErrContext) }, null)!.GetParameters()[0]
                    }
                },
                Class = global::TUnit.Core.ClassMetadata.GetOrAdd("Hoeyer.OpcUa.EndToEndTest:global::MyNamespace.ErrTest", static () => 
                {
                    var classMetadata = new global::TUnit.Core.ClassMetadata
                    {
                        Type = typeof(global::MyNamespace.ErrTest),
                        TypeInfo = new global::TUnit.Core.ConcreteType(typeof(global::MyNamespace.ErrTest)),
                        Name = "ErrTest",
                        Namespace = "MyNamespace",
                        Assembly = global::TUnit.Core.AssemblyMetadata.GetOrAdd("Hoeyer.OpcUa.EndToEndTest", static () => new global::TUnit.Core.AssemblyMetadata { Name = "Hoeyer.OpcUa.EndToEndTest" }),
                        Parameters = global::System.Array.Empty<global::TUnit.Core.ParameterMetadata>(),
                        Properties = new global::TUnit.Core.PropertyMetadata[]
                        {
                            new global::TUnit.Core.PropertyMetadata
                            {
                                ReflectionInfo = typeof(global::MyNamespace.ErrTest).GetProperty("Fixture"),
                                Type = typeof(global::MyNamespace.ErrFixture<global::MyNamespace.MyType>),
                                Name = "Fixture",
                                IsStatic = false,
                                IsNullable = false,
                                Getter = o => ((global::MyNamespace.ErrTest)o).Fixture,
                                ClassMetadata = null!,
                                ContainingTypeMetadata = null!
                            },
                            new global::TUnit.Core.PropertyMetadata
                            {
                                ReflectionInfo = typeof(global::MyNamespace.ErrTest).GetProperty("TestExecutions"),
                                Type = typeof(global::System.Collections.Generic.IEnumerable<global::System.Func<global::MyNamespace.ErrContext>>),
                                Name = "TestExecutions",
                                IsStatic = false,
                                IsNullable = false,
                                Getter = o => ((global::MyNamespace.ErrTest)o).TestExecutions,
                                ClassMetadata = null!,
                                ContainingTypeMetadata = null!
                            }
                        },
                        Parent = null
                    };
                    foreach (var prop in classMetadata.Properties)
                    {
                        prop.ClassMetadata = classMetadata;
                        prop.ContainingTypeMetadata = classMetadata;
                    }
                    return classMetadata;
                })
            },
            InstanceFactory = (typeArgs, args) => new global::MyNamespace.ErrTest()
            {
                Fixture = default!,
            },
            InvokeTypedTest = static (instance, args, cancellationToken) =>
            {
                try
                {
                    switch (args.Length)
                    {
                        case 1:
                            return new global::System.Threading.Tasks.ValueTask(instance.MyFailingTestIsHere(TUnit.Core.Helpers.CastHelper.Cast<global::MyNamespace.ErrContext>(args[0])));
                        default:
                            throw new global::System.ArgumentException($"Expected exactly 1 argument, but got {args.Length}");
                    }
                }
                catch (global::System.Exception ex)
                {
                    return new global::System.Threading.Tasks.ValueTask(global::System.Threading.Tasks.Task.FromException(ex));
                }
            },
        };
        metadata.UseRuntimeDataGeneration(testSessionId);
        yield return metadata;
        yield break;
    }
}
internal static class MyNamespace_ErrTest_MyFailingTestIsHere__ErrContext_ModuleInitializer
{
    [global::System.Runtime.CompilerServices.ModuleInitializer]
    public static void Initialize()
    {
        global::TUnit.Core.SourceRegistrar.Register(typeof(global::MyNamespace.ErrTest), new MyNamespace_ErrTest_MyFailingTestIsHere__ErrContext_TestSource());
    }
}

What would solve my problem

Either an analyser error from TUnit informing about an easy fix or for it to work automagically

[thomhurst]

I think you just need to add a data source attribute onto:

public required ErrContext Fixture ?

[TheRumle]

I think you just need to add a data source attribute onto:

public required ErrContext Fixture ?

This does not seem to resolve the problem. Even adjusting the class, I get the same error.

public class ErrFixture<T> : IAsyncDisposable, IAsyncInitializer
{ 
    [ClassDataSource<ErrContext>]
    public required ErrContext Fixture { get; set; }
    public ValueTask DisposeAsync() => ValueTask.CompletedTask;
    public Task InitializeAsync() => Task.CompletedTask;
}

[thomhurst]

@TheRumle Hopefully it should work now!

[TheRumle]

@thomhurst

Unfortunately not. Even after updating to v. 1.3.9 tThe test using "TestExecutions" as method data source, throws an exception because Fixture is null.

public class ErrTest
{
    [ClassDataSource<ErrFixture<MyType>>(Shared = SharedType.PerClass)]
    public required ErrFixture<MyType> Fixture { get; init; }
    
    public IEnumerable<Func<ErrContext>> TestExecutions => [() => Fixture.Fixture]; //accessing Fixture throws nullpointer
    
    [MethodDataSource("TestExecutions")]
    [Test]
    public async Task MyFailingTestIsHere(ErrContext context)
    {
        await Assert.That(context.GetType()).IsNotAssignableTo<MyType>();
    }
    
    [MyTestGeneratorAttribute<MyType>]
    [Test]
    public async Task MyTest2(MyType t)
    {
        await Assert.That(t.GetType()).IsAssignableTo<MyType>();
    }
}

[thomhurst]

Can you try v1.3.15 ?

[TheRumle]

@thomhurst Confirmed. Looks like its working.