使用Autofixture的CreateProxy来使用Likeness，SemanticComparison功能时遇到问题

Question

在earlier question我询问了Autofixture的CreateProxy method，potential bug被识别出来。

我不认为这个失败的测试是因为这个，而是我对Likeness.Without（...）。CreateProxy（）语法是如何工作的继续混淆。考虑下面失败的测试中，我通过创建对象的新实例，考虑到它的创作使original test非常轻微更加复杂是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 
} 

这里的乐队：

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

我的earlier question不够复杂，无法帮助我理解Likeness的一般Source。

源应该是SUT的输出，在这种情况下，它将与由AutoFixture创建的模板实例进行比较？

或者应该来源为模板由AutoFixture创建的实例，在这种情况下，它将与SUT的输出进行比较？

编辑：修正了一个错误的测试

我意识到，我已经分配了错误的template.Brass属性都的Brass和新Band实例的Strings财产。更新后的测试反映了var createdBand = new Band {Brass = template.Brass, Strings = template.Strings}的更正，现在所有六个断言都通过了。

[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

你是什么意思是：

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

在提供的例子，从Likeness生成的代理是一种从Band派生，使用语义对比算法重写Equals。

使用反射那就是：

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

更新：

的createBand和模板情况下不会受到CreateProxy方法。为什么他们应该？

对类似CreateProxy你基本上建立一个Custom Equality Assertion，可以让你做的事：

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

没有它，原来平等断言会失败：

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

然而，下面也将失败：

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

它失败了，因为th e Strings的值是来自createdBand实例的值。

这是正常现象，你可以使用Likeness直接验证：

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

输出：

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