如何为特定类自定义 AutoFixture 行为答案

【问题标题】：How do I customize AutoFixture behaviours for specific classes如何为特定类自定义 AutoFixture 行为
【发布时间】：2015-08-06 12:31:03
【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：

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？

【问题讨论】：

标签： unit-testing autofixture

【解决方案1】：

您必须为此创建自定义行为。

下面是开始：

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));
    }
}

这就是你将如何使用它：

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

注意不要删除ThrowingRecursionBehavior，因为它将用于保护其他请求，否则会抛出StackOverflowException。

但是，如果您指定的 recursionDepth 大于 1，则必须删除 ThrowingRecursionBehavior 并创建一个大于或等于 recursionDepth 的自定义。

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));

【讨论】：

【解决方案2】：

使用 Marcio Rinaldi 的答案，我为递归深度为 1 的默认情况创建了一个简单的解决方案。

internal class OmitOnRecursionBehavior<T> : ISpecimenBuilderTransformation
{
    public ISpecimenBuilder Transform(ISpecimenBuilder builder)
    {
        if (builder == null)
            throw new ArgumentNullException("builder");

        return new RecursionGuard(
            builder,
            new RecursionHandler<T>(
                new OmitOnRecursionHandler(),
                builder));
    }
}

internal class RecursionHandler<T> : IRecursionHandler
{
    private readonly IRecursionHandler handlerForRequest;
    private readonly ISpecimenBuilder builder;

    public RecursionHandler(
        IRecursionHandler handlerForRequest,
        ISpecimenBuilder builder)
    {
        if (handlerForRequest == null)
            throw new ArgumentNullException("handlerForRequest");
        if (builder == null)
            throw new ArgumentNullException("builder");

        this.handlerForRequest = handlerForRequest;
        this.builder = builder;
    }

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

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

可以这样使用：

fixture.Behaviors.Add(new OmitOnRecursionBehavior<ClassWithCircularReference>());

【讨论】：