创建具有AutoFixture递归树 [英] Creating recursive tree with AutoFixture
问题描述
我刚开始使用AutoFixture和有这种半复杂的数据结构，我想为创造一些标本。
在我与我的工作测试没太在意数据结构的内容。我只是想合理的默认值。
这个数据结构的一部分是递归的树。更具体而言，一个类认为包含本身孩子的列表的一些其它类的集合。
一个类似于：
大众A级
{
私人的IEnumerable＆LT; B＆GT; bNodes;
大众A（IEnumerable的＆LT; B＆GT; bNodes）
{
this.bNodes = bNodes;
}
}大众B级
{
私人的IEnumerable＆LT; B＆GT;儿童;
大众B（IEnumerable的＆LT; B＆GT;儿童）
{
this.children =儿童;
}
}
让我们假设我不能轻易改变这个结构因各种原因。
如果我问我的夹具，共创ThrowingRecursionBehavior将开始狂叫关于B是递归的。
如果我OmitOnRecursionBehavior取代ThrowingRecursionBehavior我得到一个ObjectCreateException。
如果我尝试类似：fixture.Inject（Enumerable.Empty（））;我得到具有相同键的项已被添加，从DictionaryFiller。如果我NullRecursionBehavior取代ThrowingRecursionBehavior同样的事情发生。
有几件事情，我想。
- 什么是创建A的样品符合BS的空列表？ 的最佳方法
- 什么是创建A的一个样本含有一些B-儿童几个孩子一些烧烤（小树）的最好方法？
有关我最后的愿望可能是好的指定一些递归深度使用Enumerable.Empty后（或零大小的数组/列表甚至可以为null）。
我知道AutoFixture是非常灵活的扩展。所以我想应该可以创造一些样本生成器，正是这一点。
事实上，我会尽量打打闹闹与自定义ISpecimenBuilder，但也许有人有一个聪明的解决方案了。
例如，它将使意义修改此行RecursionGuard：
公共对象创建（对象请求，ISpecimenContext上下文）
{
如果（this.monitoredRequests.Any（X =＆GT; this.comparer.Equals（X，请求）））
...
到
公共对象创建（对象请求，ISpecimenContext上下文）
{
如果（this.monitoredRequests.Count（X =＆GT; this.comparer.Equals（X，请求））＆GT; maxAllowedRecursions）
...
符合BS的一个空列表创建
这很容易与B的空列表创建一个实例：
VAR夹具=新灯（）;
fixture.Inject（Enumerable.Empty＆LT; B＆GT;（））;VAR一个= fixture.Create＆LT; A＆GT;（）;
创建一棵小树上
它更难以创造了一棵小树，但它是可能的。你已经在轨道与你的 RecursionGuard 的思考。为了验证是否这可能是工作，我复制大多code从 RecursionGuard 并创造了这个 DepthRecursionGuard 作为概念的证明的：
公共类DepthRecursionGuard：ISpecimenBuilderNode
{
私人只读ISpecimenBuilder建设者;
私人只读堆栈＆LT;对象＆gt; monitoredRequests; 公共DepthRecursionGuard（ISpecimenBuilder建设者）
{
如果（建设者== NULL）
{
抛出新的ArgumentNullException（助剂）;
} this.monitoredRequests =新的堆栈＆LT;对象＆gt;（）;
this.builder =建设者;
} 公共对象创建（对象请求，ISpecimenContext上下文）
{
如果（this.monitoredRequests.Count（request.Equals）→1）
返回this.HandleRecursiveRequest（请求）; this.monitoredRequests.Push（请求）;
VAR标本= this.builder.Create（请求上下文）;
this.monitoredRequests.Pop（）;
返回标本;
} 私有对象HandleRecursiveRequest（对象请求）
{
如果（typeof运算（IEnumerable的＆LT; B＆GT;）等于（申请）。）
返回Enumerable.Empty＆LT; B＆GT;（）; 抛出新的InvalidOperationException异常（嘶嘘声！）;
} 公共ISpecimenBuilderNode撰写（IEnumerable的＆LT; ISpecimenBuilder＆GT;建设者）
{
VAR建设者= ComposeIfMultiple（建筑商）;
返回新DepthRecursionGuard（制造商）;
} 公共虚拟的IEnumerator＆LT; ISpecimenBuilder＆GT;的GetEnumerator（）
{
产生回报this.builder;
} 的IEnumerator IEnumerable.GetEnumerator（）
{
返回this.GetEnumerator（）;
} 私有静态ISpecimenBuilder ComposeIfMultiple（
IEnumerable的＆LT; ISpecimenBuilder＆GT;建设者）
{
VAR isSingle = builders.Take（2）.Count之间的（）== 1;
如果（isSingle）
返回builders.Single（）; 返回新CompositeSpecimenBuilder（建筑商）;
}
}
注意改变实施创建方法，以及的IEnumerable＆LT的具体处理; B＆GT; 中 HandleRecursiveRequest 。
为了使从灯具实例此使用，我还添加了这个 DepthRecursionBehavior ：
公共类DepthRecursionBehavior：ISpecimenBuilderTransformation
{
公共ISpecimenBuilder变换（ISpecimenBuilder建设者）
{
返回新DepthRecursionGuard（制造商）;
}
}
这使我能够创建一个小的树：
VAR夹具=新灯（）;
fixture.Behaviors.OfType＆LT; ThrowingRecursionBehavior＆GT;（）
。.ToList（）的ForEach（B =＆GT; fixture.Behaviors.Remove（B））;
fixture.Behaviors.Add（新DepthRecursionBehavior（））;VAR一个= fixture.Create＆LT; A＆GT;（）;
虽然这是可能的，这是，在我看来，太辛苦了，所以我创建工作项目使其在未来更容易。
更新2013年11月13日：从AutoFixture 3.13.0，递归深度可以通过该API配置
I have just started using AutoFixture and have this semi-complex data structure that I would like to create some specimen for. In the tests I am working with I don't care too much about content of the data structure. I just want reasonable default values.
Part of this data structure is a recursive tree. More specific, one class holds a collection of some other class that contains a list of children of itself. Something akin to:
public class A
{
private IEnumerable<B> bNodes;
public A(IEnumerable<B> bNodes)
{
this.bNodes = bNodes;
}
}
public class B
{
private IEnumerable<B> children;
public B(IEnumerable<B> children)
{
this.children = children;
}
}
Lets assume I cannot easily change this structure for various reasons.
If I ask my fixture to create A ThrowingRecursionBehavior will start barking about B being recursive.
If I replace ThrowingRecursionBehavior with OmitOnRecursionBehavior I get an ObjectCreateException.
If I try something like: fixture.Inject(Enumerable.Empty()); I get "An item with the same key has already been added" from the DictionaryFiller. The same thing happens if I replace ThrowingRecursionBehavior with NullRecursionBehavior.
There are several things I would like to.
- What would be the best way to create a specimen of A with an empty list of Bs?
- What would be the best way to create a specimen of A with a few Bs containing a few B-children with a few children (a small tree)?
For my last wish it could be nice to specify some recursion depth after which Enumerable.Empty was used (or a zero sized array / List or even null). I know that AutoFixture is very flexible to extend. So I suppose it should be possible to create some specimen builder that does exactly this. In fact I will try fooling around with a custom ISpecimenBuilder, but perhaps someone has a smarter solution already. For example, would it make sense to modify this line in RecursionGuard:
public object Create(object request, ISpecimenContext context)
{
if (this.monitoredRequests.Any(x => this.comparer.Equals(x, request)))
...
to
public object Create(object request, ISpecimenContext context)
{
if (this.monitoredRequests.Count(x => this.comparer.Equals(x, request)) > maxAllowedRecursions)
...
Creating A with an empty list of Bs
It's easy to create an instance of A with an empty list of Bs:
var fixture = new Fixture();
fixture.Inject(Enumerable.Empty<B>());
var a = fixture.Create<A>();
Creating a small tree
It's much more difficult to create a small tree, but it's possible. You're already on track with your thinking about RecursionGuard. In order to verify if this could work, I copied most of the code from RecursionGuard and created this DepthRecursionGuard as a proof of concept:
public class DepthRecursionGuard : ISpecimenBuilderNode
{
private readonly ISpecimenBuilder builder;
private readonly Stack<object> monitoredRequests;
public DepthRecursionGuard(ISpecimenBuilder builder)
{
if (builder == null)
{
throw new ArgumentNullException("builder");
}
this.monitoredRequests = new Stack<object>();
this.builder = builder;
}
public object Create(object request, ISpecimenContext context)
{
if (this.monitoredRequests.Count(request.Equals) > 1)
return this.HandleRecursiveRequest(request);
this.monitoredRequests.Push(request);
var specimen = this.builder.Create(request, context);
this.monitoredRequests.Pop();
return specimen;
}
private object HandleRecursiveRequest(object request)
{
if (typeof(IEnumerable<B>).Equals(request))
return Enumerable.Empty<B>();
throw new InvalidOperationException("boo hiss!");
}
public ISpecimenBuilderNode Compose(IEnumerable<ISpecimenBuilder> builders)
{
var builder = ComposeIfMultiple(builders);
return new DepthRecursionGuard(builder);
}
public virtual IEnumerator<ISpecimenBuilder> GetEnumerator()
{
yield return this.builder;
}
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
private static ISpecimenBuilder ComposeIfMultiple(
IEnumerable<ISpecimenBuilder> builders)
{
var isSingle = builders.Take(2).Count() == 1;
if (isSingle)
return builders.Single();
return new CompositeSpecimenBuilder(builders);
}
}
Notice the changed implementation of the Create method, as well as the specific handling of IEnumerable<B> in HandleRecursiveRequest.
In order to make this usable from a Fixture instance, I also added this DepthRecursionBehavior:
public class DepthRecursionBehavior : ISpecimenBuilderTransformation
{
public ISpecimenBuilder Transform(ISpecimenBuilder builder)
{
return new DepthRecursionGuard(builder);
}
}
This enabled me to create a small tree:
var fixture = new Fixture();
fixture.Behaviors.OfType<ThrowingRecursionBehavior>()
.ToList().ForEach(b => fixture.Behaviors.Remove(b));
fixture.Behaviors.Add(new DepthRecursionBehavior());
var a = fixture.Create<A>();
While this is possible, it's, in my opinion, too hard, so I've created a work item to make it easier in the future.
Update 2013.11.13: From AutoFixture 3.13.0, the recursion depth can be configured via that API.
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