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自定义FsCheck输出

fscheck f#

Friedrich Gretz · 技术社区 · 8 年前

目前的问题是:我设法生成了随机图(用于测试一些图功能),但当测试失败时,FsCheck会吐出整个图,并且它不使用ToString,因此它实际上会转储原始记录列表,您在其中看不到任何内容。

那么,我如何更改FsCheck的输出行为,以便

实际上在输入图上调用我的ToString方法
输出更多信息

module GraphProperties

open NUnit.Framework
open FsCheck
open FsCheck.NUnit

let generateRandomGraph =
    gen {
        let graph: Graph<int,int> = Graph<_,_>.Empty()
        // fill in random nodes and transitions...
        return graph
    }

type MyGenerators =
    static member Graph() =
        {new Arbitrary<Graph<int,int>>() with
            override this.Generator = generateRandomGraph
            override this.Shrinker _ = Seq.empty }

[<TestFixture>]
type NUnitTest() =
    [<Property(Arbitrary=[|typeof<MyGenerators>|], QuietOnSuccess = true)>]
    member __.cloningDoesNotChangeTheGraph (originalGraph: Graph<int,int>) =
        let newGraph = clone originalGraph
        newGraph = originalGraph

2 回复 | 直到 8 年前

rmunn 8 年前

FsCheck使用 sprintf "%A" %A 格式化程序。根据 How do I customize output of a custom type using printf? ,方法是使用 StructuredFormatDisplay attribute PreText {PropertyName} PostText 哪里 PropertyName 应该是一个属性( 不函数!)根据你的类型。E、例如,假设你有一个树结构,叶子中有一些复杂的信息,但在测试中,你只需要知道叶子的数量,而不需要知道叶子中有什么。因此,您可以从以下数据类型开始:

// Example 1
type ComplicatedRecord = { ... }
type Tree =
    | Leaf of ComplicatedRecord
    | Node of Tree list
    with
        member x.LeafCount =
            match x with
            | Leaf _ -> 1
            | Node leaves -> leaves |> List.sumBy (fun x -> x.LeafCount)
        override x.ToString() =
            // For test output, we don't care about leaf data, just count
            match x with
            | Leaf -> "Tree with a total of 1 leaf"
            | Node -> sprintf "Tree with a total of %d leaves" x.LeafCount

不 %A 声明了格式,所以FsCheck(以及使用 sprintf“%A” 所有物 ,不是函数( ToString

// Example 2
type ComplicatedRecord = { ... }
[<StructuredFormatDisplay("{LeafCountAsString}")>]
type Tree =
    | Leaf of ComplicatedRecord
    | Node of Tree list
    with
        member x.LeafCount =
            match x with
            | Leaf _ -> 1
            | Node leaves -> leaves |> List.sumBy (fun x -> x.LeafCount)
        member x.LeafCountAsString = x.ToString()
        override x.ToString() =
            // For test output, we don't care about leaf data, just count
            match x with
            | Leaf -> "Tree with a total of 1 leaf"
            | Node -> sprintf "Tree with a total of %d leaves" x.LeafCount

注意:我没有在F#中测试它,只是在堆栈溢出注释框中键入了它——所以可能是我弄乱了 ToString() with 关键字)。但我知道 结构化格式显示

顺便说一句,你也可以设置一个 结构化格式显示

// Example 3
[<StructuredFormatDisplay("LeafRecord")>] // Note no {} and no property
type ComplicatedRecord = { ... }
type Tree =
    | Leaf of ComplicatedRecord
    | Node of Tree list
    with
        member x.LeafCount =
            match x with
            | Leaf _ -> 1
            | Node leaves -> leaves |> List.sumBy (fun x -> x.LeafCount)
        override x.ToString() =
            // For test output, we don't care about leaf data, just count
            match x with
            | Leaf -> "Tree with a total of 1 leaf"
            | Node -> sprintf "Tree with a total of %d leaves" x.LeafCount

现在你所有的 ComplicatedRecord 实例,无论其内容如何,都将显示为文本 LeafRecord 结构化格式显示 Tree 类型

这不是一个完全理想的解决方案,因为您可能需要调整

Kurt Schelfthout 8 年前

https://fscheck.github.io/FsCheck/Properties.html#And-Or-and-Labels