Question

我在nUnit中发现了一些奇怪的行为吗？

以下VB.Net测试失败：

strcpy(msgf, g_fxn());

Test 'SameAsTest.UseSameAs' failed: 
  Expected string length 19 but was 29. Strings differ at index 19.
  Expected: "Prop1 Get,Prop1 Get"
  But was:  "Prop1 Get,Prop1 Get,Prop1 Set"

  ------------------------------^
    SameAsTest.vb(33,0): at SameAsTest.UseSameAs()

1 passed, 1 failed, 0 skipped, took 1.80 seconds (NUnit 2.5.5).

当c＃equiv正常工作时：

Option Strict On

Imports System
Imports System.Collections.Generic
Imports NUnit.Framework

<TestFixture()>
Public Class SameAsTest

    Private CallHistory As List(Of String)
    Private mPropValue As String = "ThisIsIt"


    Public Property Prop1 As String
        Get
            CallHistory.Add("Prop1 Get")
            Return mPropValue
        End Get
        Set(ByVal value As String)
            CallHistory.Add("Prop1 Set")
            mPropValue = value
        End Set
    End Property

    <SetUp()>
    Public Sub Setup()
        CallHistory = New List(Of String)
    End Sub

    <Test()>
    Public Sub UseSameAs()
        Assert.That(Prop1, [Is].SameAs(Prop1))
        Assert.That(String.Join(",", CallHistory.ToArray()), [Is].EqualTo("Prop1 Get,Prop1 Get"))
    End Sub

    <Test()>
    Public Sub UseAreSame()
        Assert.AreSame(Prop1, Prop1)
        Assert.That(String.Join(",", CallHistory.ToArray()), [Is].EqualTo("Prop1 Get,Prop1 Get"))
    End Sub
End Class

2 passed, 0 failed, 0 skipped, took 0.19 seconds (NUnit 2.5.5).

Answer 1

问题实际上是对SameAs的调用。问题是属性是作为Assert.That调用的第一个参数传递的。

Assert.That有许多不同的重载，事实证明，在VB到C＃中，重载决策的执行方式不同。在C＃中，属性与以下内容匹配：

Asset.That(object actual, IResolveConstraint expression);

在VB中，它被匹配：

Assert.That<Of T>(ByRef T actual, IResolveConstraint express);

由于VB版本实际上是将非引用属性值传递给期望引用的方法，因此它似乎通过创建本地字符串来模拟引用传递，通过引用将其传递给方法然后设置属性的值到字符串的返回值。我不确定它为什么选择这种方式，硬核VB程序员可能会解释它。

您可以通过声明局部变量并将其用于第一个参数来解决它：

Dim prop1 = Prop1
Assert.That(prop1, [Is].SameAs(Prop1))

或者通过强制转换参数来强制它使用That方法的预期重载。

Assert.That(CType(Prop1, Object), [Is].SameAs(Prop1))

SameAs Assertion使用VB.Net调用setter

1 个答案: