使用Autofixture的CreateProxy來使用Likeness，SemanticComparison功能時遇到問題

Question

在earlier question我詢問了Autofixture的CreateProxy method，potential bug被識別出來。

我不認爲這個失敗的測試是因爲這個，而是我對Likeness.Without（...）。CreateProxy（）語法是如何工作的繼續混淆。考慮下面失敗的測試中，我通過創建對象的新實例，考慮到它的創作使original test非常輕微更加複雜是SUT：

[Fact] 
public void Equality_Behaves_As_Expected() 
{ 
    // arrange: intent -> use the fixture-created Band as Object Mother 
    var template = new Fixture().Create<Band>(); 

    // act: intent -> instantiated Band *is* the SUT 
    var createdBand = new Band {Brass = template.Brass, 
           Strings = template.Brass}; 

    // intent -> specify that .Brass should not be considered in comparison 
    var likeness = template.AsSource().OfLikeness<Band>(). 
     Without(x => x.Brass).CreateProxy(); // Ignore .Brass property 

    // per [https://stackoverflow.com/a/15476108/533958] explicity assign 
    // properties to likeness 
    likeness.Strings = template.Strings; 
    likeness.Brass = "foo"; // should be ignored 

    // assert: intent -> check equality between created Band & template Band 
    //   to include all members not excluded in likeness definition 
    likeness.Should().Be(createdBand);   // Fails 
    likeness.ShouldBeEquivalentTo(createdBand); // Fails 
    Assert.True(likeness.Equals(createdBand)); // Fails 
} 

這裏的樂隊：

public class Band 
{ 
    public string Strings { get; set; } 
    public string Brass { get; set; } 
} 

我的earlier question不夠複雜，無法幫助我理解Likeness的一般Source。

源應該是SUT的輸出，在這種情況下，它將與由AutoFixture創建的模板實例進行比較？

或者應該來源爲模板由AutoFixture創建的實例，在這種情況下，它將與SUT的輸出進行比較？

編輯：修正了一個錯誤的測試

我意識到，我已經分配了錯誤的template.Brass屬性都的Brass和新Band實例的Strings財產。更新後的測試反映了var createdBand = new Band {Brass = template.Brass, Strings = template.Strings}的更正，現在所有六個斷言都通過了。

[Fact] 
public void Equality_Behaves_As_Expected() 
{ 
    // arrange: intent -> use the fixture-created Band as Object Mother 
    var template = new Fixture().Create<Band>(); 

    // act: intent -> instantiated Band *is* the SUT 
    var createdBand = new Band {Brass = template.Brass, Strings = template.Strings}; 

    // likeness of created 
    var createdLikeness = createdBand.AsSource().OfLikeness<Band>(). 
     Without(x => x.Brass).CreateProxy(); // .Brass should not be considered in comparison 

    // https://stackoverflow.com/a/15476108/533958 (explicity assign properties to likeness) 
    createdLikeness.Strings = createdBand.Strings; 
    createdLikeness.Brass = "foo"; // should be ignored 

    // likeness of template 
    var templateLikeness = template.AsSource().OfLikeness<Band>() 
     .Without(x => x.Brass) 
     .CreateProxy(); 
    templateLikeness.Strings = template.Strings; 
    templateLikeness.Brass = "foo"; 

    // assert: intent -> compare created Band to template Band 
    createdLikeness.Should().Be(template); 
    createdLikeness.ShouldBeEquivalentTo(template); 
    Assert.True(createdLikeness.Equals(template)); 

    templateLikeness.Should().Be(createdBand); 
    templateLikeness.ShouldBeEquivalentTo(createdBand); 
    Assert.True(templateLikeness.Equals(createdBand)); 
} 

Answer 1

你是什麼意思是：

likeness.Should().BeAssignableTo<Band>(); // Returns true. 

在提供的例子，從Likeness生成的代理是一種從Band派生，使用語義對比算法重寫Equals。

使用反射那就是：

createdBand.GetType().IsAssignableFrom(likeness.GetType()) // Returns true. 

更新：

的createBand和模板情況下不會受到CreateProxy方法。爲什麼他們應該？

對類似CreateProxy你基本上建立一個Custom Equality Assertion，可以讓你做的事：

Assert.True(likeness.Equals(createdBand)); // Passed. 

沒有它，原來平等斷言會失敗：

Assert.True(template.Equals(createdBand)); // Failed. 

然而，下面也將失敗：

Assert.True(likeness.Equals(template)); 

它失敗了，因爲th e Strings的值是來自createdBand實例的值。

這是正常現象，你可以使用Likeness直接驗證：

createdBand.AsSource().OfLikeness<Band>() 
    .Without(x => x.Brass).ShouldEqual(template); 

輸出：

The provided value `Band` did not match the expected value `Band`. The following members did not match: 
     - Strings.