c# - AutoFixture:配置开放式泛型样本生成器

Question

我有一个使用开放泛型的对象模型(是的，是的，现在我有两个问题；这就是我来这里的原因:) :-

public interface IOGF<T>
{
}

class C
{
}

class D
{
    readonly IOGF<C> _ogf;

    public D( IOGF<C> ogf )
    {
        _ogf = ogf;
    }
} 

我正在尝试让 AutoFixture 生成 D 的匿名实例多于。但是，就其本身而言，AutoFixture 没有构建 IOGF<> 的内置策略。因此我们观察到:

public class OpenGenericsBinderDemo
{
    [Fact]
    public void X()
    {
        var fixture = new Fixture();

        Assert.Throws<Ploeh.AutoFixture.ObjectCreationException>( () =>
            fixture.CreateAnonymous<D>() );
    }

底层消息是:

Ploeh.AutoFixture.ObjectCreationException : AutoFixture was unable to create an instance from IOGF`1[C], most likely because it has no public constructor, is an abstract or non-public type.

我很乐意为它提供一个具体的实现:

public class OGF<T> : IOGF<T>
{
    public OGF( IX x )
    {
    }
}

public interface IX
{
}

public class X : IX
{
}

和关联的绑定(bind):

fixture.Register<IX,X>();

我如何(或者我应该这样看待问题？？)让下面的测试通过？

public class OpenGenericsLearning
{
    [Fact]
    public void OpenGenericsDontGetResolved()
    {
        var fixture = new Fixture();
        fixture.Inject<IX>( fixture.Freeze<X>() );

        // TODO register or do something that will provide 
        //      OGF<C> to fulfill D's IOGF<C> requirement

        Assert.NotNull( fixture.CreateAnonymous<D>());
    }
}

(在 codeplex 站点上有关于此的讨论和问题 - 我只需要快速实现这一点，如果这只是一个坏主意和/或我错过了一些东西，我愿意删除它)

编辑 2:(另请参阅对 Mark 的回答的评论)这里的(公认的人为的)上下文是对大型“几乎完整系统”的被测系统对象图而不是小型(受控/易于理解 :) 的验收测试单元或集成测试场景中的一对或三组类。正如在 self 提问的附加陈述中提到的，我并不完全相信这种类型的测试是否有意义。

Answer 1

您可以创建一个按如下方式工作的自定义:

public class AnOpenGenericsBinderDemo
{
    [Fact]
    public void RegisteringAGenericBinderShouldEnableResolution()
    {
        var fixture = new Fixture();
        fixture.Inject<IX>( fixture.Freeze<X>() );
        fixture.RegisterOpenGenericImplementation( typeof( IOGF<> ), typeof( OGF<> ) );

        Assert.IsType<OGF<C>>( fixture.CreateAnonymous<D>().Ogf );
    }
}

并且是这样实现的:

public static class AutoFixtureOpenGenericsExtensions
{
    public static void RegisterOpenGenericImplementation( this IFixture that, Type serviceType, Type componentType )
    {
        if ( !serviceType.ContainsGenericParameters )
            throw new ArgumentException( "must be open generic", "serviceType" );
        if ( !componentType.ContainsGenericParameters )
            throw new ArgumentException( "must be open generic", "componentType" );
        // TODO verify number of type parameters is 1 in each case
        that.Customize( new OpenGenericsBinderCustomization( serviceType, componentType ) );
    }

    public class OpenGenericsBinderCustomization : ICustomization
    {
        readonly Type _serviceType;
        readonly Type _componentType;

        public OpenGenericsBinderCustomization( Type serviceType, Type componentType )
        {
            _serviceType = serviceType;
            _componentType = componentType;
        }

        void ICustomization.Customize( IFixture fixture )
        {
            fixture.Customizations.Add( new OpenGenericsSpecimenBuilder( _serviceType, _componentType ) );
        }

        class OpenGenericsSpecimenBuilder : ISpecimenBuilder
        {
            readonly Type _serviceType;
            readonly Type _componentType;

            public OpenGenericsSpecimenBuilder( Type serviceType, Type componentType )
            {
                _serviceType = serviceType;
                _componentType = componentType;
            }

            object ISpecimenBuilder.Create( object request, ISpecimenContext context )
            {
                var typedRequest = request as Type;
                if ( typedRequest != null && typedRequest.IsGenericType && typedRequest.GetGenericTypeDefinition() == _serviceType )
                    return context.Resolve( _componentType.MakeGenericType( typedRequest.GetGenericArguments().Single() ) );
                return new NoSpecimen( request );
            }
        }
    }
}

我假设有人有比这更好的实现和/或有一个内置的实现。

编辑:以下是具有传感属性的更新 D:

class D
{
    readonly IOGF<C> _ogf;

    public D( IOGF<C> ogf )
    {
        _ogf = ogf;
    }

    public IOGF<C> Ogf
    {
        get { return _ogf; }
    }
}