如何在单元测试编码实现类的访问器？这里给出一个答案

通常单元测试需要访问受测类的私有方法或属性，一般需要使用VSTS自动生成的访问器，但是对于该类的父类私有属性就无法访问了，这也是上一篇博文提到的状况。其实我们还可以自己编写访问器，这样就不需要受到系统生成的访问器的束缚（由于生成的访问器没有源码无法修改）。下文就是一个范例（受测项目BankDemo.csproj，程序集BankDemo.exe）：

＝＝＝＝＝＝＝＝受测类的实现代码：＝＝＝＝＝＝＝＝

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;

namespace  BankDemo
{
     public   class  BankAccount
    {
         private   int  _accountNo;
         private   float  _currentBalance;
         private   static   float  _bankAsset;
         private   static   int  _newUniqueAccountNo;

         private   static   int  GetUniqueAccountNo
        {
             get  {  return   ++ _newUniqueAccountNo; }
        }

         private   float  CurrentBalance
        {
             get  {  return  _currentBalance; }
             set  { _currentBalance  =  value; }
        }

         //  Constructors for new account
         private  BankAccount( float  initialBalance)
        {
             this ._accountNo  =  GetUniqueAccountNo;
             this ._currentBalance  =  initialBalance;
            _bankAsset  +=  initialBalance;
        }

         //  Methods
         private   float  DepositMoney( float  depositAmount)
        {
             this .CurrentBalance  +=  depositAmount;
            _bankAsset  +=  depositAmount;
             return   this .CurrentBalance;
        }

         private   float  WithdrawMoney( float  withdrawAmount)
        {
             this .CurrentBalance  -=  withdrawAmount;
            _bankAsset  -=  withdrawAmount;
             return   this .CurrentBalance;
        }

         private   static   float  BankAsset()
        {
             return  _bankAsset;
        }

    }


}

 

＝＝＝＝＝＝＝＝访问器代码可以这样实现：＝＝＝＝＝＝＝＝  

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.VisualStudio.TestTools.UnitTesting;


namespace TestProject1
{
    class BankAccountAccessor
    {
        PrivateObject _privateObject;
        static PrivateType _privateType = new PrivateType("BankDemo", "BankDemo.BankAccount");


        public BankAccountAccessor(object target)
        {
            _privateObject = new PrivateObject(target, _privateType);
        }


        public static object CreatePrivate(float initialBalance)
        {
            object[] args = new object[] { initialBalance };
            PrivateObject priv_obj = new PrivateObject("BankDemo", "BankDemo.BankAccount", new System.Type[] { typeof(float) }, args);
            return priv_obj.Target;
        }

        public float DepositMoney(float depositAmount)
        {
            object[] args = new object[] { depositAmount };

            return ((float)(_privateObject.Invoke("DepositMoney", new Type[] { typeof(float) }, args)));
        }

        public float WithdrawMoney(float withdrawAmount)
        {
            object[] args = new object[] { withdrawAmount };

            return ((float)(_privateObject.Invoke("WithdrawMoney", new Type[] { typeof(float) }, args)));
        }

        public static float BankAsset()
        {
            object[] args = new object[0];

            return ((float)(_privateType.InvokeStatic("BankAsset", new System.Type[0], args)));
        }

        public float CurrentBalance
        {
            get {     return ((float)(_privateObject.GetProperty("CurrentBalance")));     }

            set {     _privateObject.SetProperty("CurrentBalance", value);     }
        }

        public static int GetUniqueAccountNo
        {
            get {     return ((int)(_privateType.GetStaticProperty("GetUniqueAccountNo")));     }
        }

        public int _accountNo
        {
            get { return ((int)(_privateObject.GetField("_accountNo"))); }

            set { _privateObject.SetField("_accountNo", value); }
        }
    }
}

 

＝＝＝＝＝＝＝＝单元测试就是如下（这里仅仅举其中一个私有方法测试为例）：＝＝＝＝＝＝＝＝

 

[TestMethod()]
public   void  WithdrawMoneyTest()
{
             float  initBalance  =  5000f;
             object  param0  =  BankAccountAccessor.CreatePrivate(initBalance);
            BankAccountAccessor target  =   new  BankAccountAccessor(param0);
             float  withdrawAmount  =  100F;
             float  expected  =  initBalance  -  withdrawAmount;
             float  actual;
            actual  =  target.WithdrawMoney(withdrawAmount);
            Assert.AreEqual(expected, actual);
}