使用VB.Net的SameAs断言调用setter

本文关键字：断言 调用 setter SameAs VB Net 使用 | 更新日期: 2023-09-27 18:01:28

我发现一些奇怪的行为在nUnit?

下面的VB。Net测试失败:

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).

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

当c#代码正常工作时:

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

using System;
using System.Collections.Generic;
using NUnit.Framework ;
    [TestFixture ]
    class Dummy
    {
        private List<String> CallHistory;
        private String mPropValue = "ThisIsIt";
        [SetUp]
        public void Setup()
        {
            CallHistory = new List<string>();
        }
        public String Prop1 
        {
            get
            {
            CallHistory.Add("Prop1 Get");
            return mPropValue;
            }
            set
            {
                CallHistory.Add("Prop1 Set");
                mPropValue = value;
            }
        }
        [Test]
        public void UseSameAs()
        {
            Assert.That(Prop1, Is.SameAs(Prop1));
            Assert.That(String.Join(",", CallHistory.ToArray()), Is.EqualTo("Prop1 Get,Prop1 Get"));
        }
        [Test]
        public void UseaAreSame()
        {
            Assert.AreSame(Prop1, Prop1);
            Assert.That(String.Join(",", CallHistory.ToArray()), Is.EqualTo("Prop1 Get,Prop1 Get"));
        }
}

使用VB.Net的SameAs断言调用setter

问题实际上不是对SameAs的调用。问题是该属性被作为Assert.That调用的第一个参数传递。

Assert.That有许多不同的重载，事实证明，在VB和c#中重载分辨率是不同的。在c#中，该属性是针对:

进行匹配的。
Asset.That(object actual, IResolveConstraint expression);

在VB中，它被匹配为:

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，它似乎是通过创建一个本地字符串来模拟引用传递，通过引用将其传递到方法中，然后将属性的值设置为字符串的返回值。我不确定为什么它选择这样的函数，硬核的VB程序员可能能够解释它。

您可以通过声明一个局部变量并将其用于第一个参数来绕过它: 
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))
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