如何为特定类自定义 AutoFixture 行为 [英] How do I customize AutoFixture behaviours for specific classes

问题描述

我需要启用 AutoFixture 以创建具有循环引用的类型实例(来自第三方提供的 API).为此，我可以删除默认的 ThrowingRecursionBehavior，如下所示:

I need to enable AutoFixture to create instances of types with circular references (from an API provided by a third party). To do this I can remove the default ThrowingRecursionBehavior as shown below:

public class RecursiveObjectCustomization : ICustomization
{
    public void Customize(IFixture fixture)
    {
        fixture.Behaviors.OfType<ThrowingRecursionBehavior>()
            .ToList()
            .ForEach(b => fixture.Behaviors.Remove(b));
        fixture.Behaviors.Add(new OmitOnRecursionBehavior());
    }
 }

但是，我知道当通过属性应用自定义时，这将删除所有类型的 ThrowingRecursionBehavior.如何将修改后的行为限制为仅适用于特定类型?

However, I understand that this will remove the ThrowingRecursionBehavior for all types when the customization is applied via an attribute. How can I limit the modified behavior to only apply to the specific types?

推荐答案

您必须为此创建自定义行为.

You'll have to create a custom behavior for that.

这里有一些开始:

public class OmitOnRecursionForRequestBehavior : ISpecimenBuilderTransformation
{
    private const int DefaultRecursionDepth = 1;
    private readonly int recursionDepth;
    private readonly object request;

    public OmitOnRecursionForRequestBehavior(object request)
        : this(request, DefaultRecursionDepth)
    {
    }

    public OmitOnRecursionForRequestBehavior(
        object request,
        int recursionDepth)
    {
        if (request == null)
            throw new ArgumentNullException("request");
        if (recursionDepth < 1)
            throw new ArgumentOutOfRangeException(
                "recursionDepth",
                "Recursion depth must be greater than 0.");

        this.recursionDepth = recursionDepth;
        this.request = request;
    }

    public ISpecimenBuilder Transform(ISpecimenBuilder builder)
    {
        if (builder == null)
            throw new ArgumentNullException("builder");

        return new RecursionGuard(
            builder,
            new RecursionForRequestHandler(
                request,
                new OmitOnRecursionHandler(),
                builder),
            recursionDepth);
    }
}

public class RecursionForRequestHandler : IRecursionHandler
{
    private readonly object request;
    private readonly IRecursionHandler handlerForRequest;
    private readonly ISpecimenBuilder handler;

    public RecursionForRequestHandler(
        object request,
        IRecursionHandler handlerForRequest,
        ISpecimenBuilder handler)
    {
        if (request == null)
            throw new ArgumentNullException("request");
        if (handlerForRequest == null)
            throw new ArgumentNullException("handlerForRequest");
        if (handler == null)
            throw new ArgumentNullException("handler");

        this.request = request;
        this.handlerForRequest = handlerForRequest;
        this.handler = handler;
    }

    public object HandleRecursiveRequest(
        object request,
        IEnumerable<object> recordedRequests)
    {
        if (this.request.Equals(request))
            return handlerForRequest.HandleRecursiveRequest(
                request,
                recordedRequests);

        return handler.Create(request, new SpecimenContext(handler));
    }
}

这是你将如何使用它:

fixture.Behaviors.Add(new OmitOnRecursionForRequestBehavior(typeof(MyType)));
fixture.Behaviors.Add(new OmitOnRecursionForRequestBehavior(typeof(AnotherType)));

请注意，不要删除 ThrowingRecursionBehavior，因为它将用于保护其他请求，否则将抛出 StackOverflowException.

Note that you don't remove the ThrowingRecursionBehavior as it will be used to guard the other requests, otherwise a StackOverflowException will be thrown.

但是，如果您指定的 recursionDepth 大于 1，则必须删除 ThrowingRecursionBehavior 并创建一个具有更大或等于 recursionDepth 的自定义.

However, if you specify a recursionDepth greater than 1, you'll have to remove the ThrowingRecursionBehavior and create a customized one with a greater or equal recursionDepth.

public class DepthThrowingRecursionBehavior : ISpecimenBuilderTransformation
{
    private readonly int recursionDepth;

    public DepthThrowingRecursionBehavior(int recursionDepth)
    {
        if (recursionDepth < 1)
            throw new ArgumentOutOfRangeException(
                "recursionDepth",
                "Recursion depth must be greater than 0.");

        this.recursionDepth = recursionDepth;
    }

    public ISpecimenBuilder Transform(ISpecimenBuilder builder)
    {
        if (builder == null)
            throw new ArgumentNullException("builder");

        return new RecursionGuard(
            builder,
            new ThrowingRecursionHandler(),
            recursionDepth);
    }
}

fixture.Behaviors.OfType<ThrowingRecursionBehavior>()
    .ToList()
    .ForEach(b => fixture.Behaviors.Remove(b));
fixture.Behaviors.Add(new DepthThrowingRecursionBehavior(2));
fixture.Behaviors.Add(new OmitOnRecursionForRequestBehavior(typeof(MyType), 2));
fixture.Behaviors.Add(new OmitOnRecursionForRequestBehavior(typeof(AnotherType), 1));

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