單元測試 – 使用Fake Object

抽取相依的物件並且覆寫

下面是一個範例，這個範例的SUT是Holiday.cs，如果今天是9/1就傳HappyBirthday，否則就傳No
因為單元測試應該要能夠具有隔離的特性，不可因為今天的日期不一樣而有不同的結果
所以”取得今天日期”，就會讓程式碼變得不可測試。

在下面的範例裡，我們可以看見如何使用假物件去測試不可測試的程式碼：
Holiday.cs

using System;

namespace TestProject1
{
    public class Holiday
    {
        public string IsTodayJoeyBirthday()
        {
            var date = GetToday();
            return (date.Month == 9 && date.Day == 1) ? "HappyBirthday" : "No";
        }
        //將有相依的部份抽出來
        protected virtual DateTime GetToday()
        {
            return DateTime.Today;
        }
    }
}

using System;

namespace TestProject1

{

public class Holiday

{

public string IsTodayJoeyBirthday()

{

var date = GetToday();

return (date.Month == 9 && date.Day == 1) ? "HappyBirthday" : "No";

}

//將有相依的部份抽出來

protected virtual DateTime GetToday()

{

return DateTime.Today;

}

Test2Cs.cs

using System;
using NUnit.Framework;
using TestProject1;

namespace TestProject1
{
    [TestFixture]
    public class Test2Cs
    { 
        [Test]
        public void today_is_not_joey_birthday()
        {
            var target = new HolidayForTest();
            target.SetToday(new DateTime(2015,1,1));
            Assert.AreEqual(target.IsTodayJoeyBirthday(), "No");
        }
        
        [Test]
        public void today_is_joey_birthday()
        {
            var target = new HolidayForTest();
            target.SetToday(new DateTime(2015,9,1));
            Assert.AreEqual(target.IsTodayJoeyBirthday(), "HappyBirthday");
        }
    }
}
//創建一個假物件並且繼承Holiday，替換掉取得今日日期這件事
internal class HolidayForTest : Holiday
{
    private DateTime _today;
    protected override DateTime GetToday()
    {
        return _today;
    }

    public void SetToday(DateTime date)
    {
        _today = date;
    }
}

using System;

using NUnit.Framework;

using TestProject1;

namespace TestProject1

{

[TestFixture]

public class Test2Cs

{

[Test]

public void today_is_not_joey_birthday()

{

var target = new HolidayForTest();

target.SetToday(new DateTime(2015,1,1));

Assert.AreEqual(target.IsTodayJoeyBirthday(), "No");

}

[Test]

public void today_is_joey_birthday()

{

var target = new HolidayForTest();

target.SetToday(new DateTime(2015,9,1));

Assert.AreEqual(target.IsTodayJoeyBirthday(), "HappyBirthday");

}

//創建一個假物件並且繼承Holiday，替換掉取得今日日期這件事

internal class HolidayForTest : Holiday

{

private DateTime _today;

protected override DateTime GetToday()

{

return _today;

}

public void SetToday(DateTime date)

{

_today = date;

}

如何對現行沒有測試的PROD CODE加上unit test

這一個測試的重點在於：針對依賴的code，找出不可控制的地方並抽出來

找到不可控制的依賴
抽出方法
把private改成protect virtual
在測試專案新增子類繼承SUT
override protected方法並加開set方法
測試SUT改測子類
set依賴的值

使用依賴注入

使用依賴注入來達成低藕合高內聚的程式碼
1. 針對相依的物件抽出interface，針對相依的值抽出field
2. 產生contructor，選要注入的field去依賴注入
3. 產生無參數的constructor，確保本來的程式無誤
4. 測試程式新增fake物件做interface，決定行為並注入SUT

所謂低藕合高內聚的程式碼也可以讓程式更容易被測試

用Fake Object來取代相依物件的方法

如果測試的資料都是固定的，可以在測試裡面創建假物件來注入SUT（測試目標）

以下為範例程式
AuthenticationServiceTests.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//using Microsoft.VisualStudio.TestTools.UnitTesting;
using NUnit.Framework;
using RsaSecureToken;
using Assert = NUnit.Framework.Assert;

namespace RsaSecureToken.Tests
{
    [TestFixture]
    public class AuthenticationServiceTests
    {
        [Test()]
        public void IsValidTest()
        {
            var target = new AuthenticationService(new FakeProfile(), new FakeToken());

            var actual = target.IsValid("joey", "91000000");

            //always failed
            Assert.IsTrue(actual);                       
        }
    }

    public class FakeProfile:IProfile
    {
        
        public string GetPassword(string account)
        {
            if (account == "joey")
            {
                return "91";
            }

            throw new Exception();
        }
    }
    
    public class FakeToken:IRsaToken
    {
        public string GetRandom(string account)
        {
            return "000000";
        }
    }
}

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

//using Microsoft.VisualStudio.TestTools.UnitTesting;

using NUnit.Framework;

using RsaSecureToken;

using Assert = NUnit.Framework.Assert;

namespace RsaSecureToken.Tests

{

[TestFixture]

public class AuthenticationServiceTests

{

[Test()]

public void IsValidTest()

{

var target = new AuthenticationService(new FakeProfile(), new FakeToken());

var actual = target.IsValid("joey", "91000000");

//always failed

Assert.IsTrue(actual);

}

public class FakeProfile:IProfile

{

public string GetPassword(string account)

{

if (account == "joey")

{

return "91";

}

throw new Exception();

}

public class FakeToken:IRsaToken

{

public string GetRandom(string account)

{

return "000000";

}

AuthenticationService.cs

using System;
using System.Collections.Generic;

namespace RsaSecureToken
{
    public class AuthenticationService
    {
        private IProfile _profileDao;
        private IRsaToken _rsaToken;

        public AuthenticationService()
        {
            _profileDao = new ProfileDao();
            _rsaToken = new RsaTokenDao();
        }
        //for test
        public AuthenticationService(IProfile profile, IRsaToken rsaToken)
        {
            _profileDao = profile;
            _rsaToken = rsaToken;
        }
        
        public bool IsValid(string account, string password)
        {
            // 根據 account 取得自訂密碼
            var passwordFromDao = _profileDao.GetPassword(account);

            // 根據 account 取得 RSA token 目前的亂數
            var randomCode = _rsaToken.GetRandom(account);

            // 驗證傳入的 password 是否等於自訂密碼 + RSA token亂數
            var validPassword = passwordFromDao + randomCode;
            var isValid = password == validPassword;

            if (isValid)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }

    public interface IProfile
    {
        string GetPassword(string account);
    }

    public class ProfileDao : IProfile
    {
        public string GetPassword(string account)
        {
            return Context.GetPassword(account);
        }
    }

    public static class Context
    {
        public static Dictionary<string, string> profiles;

        static Context()
        {
            profiles = new Dictionary<string, string>();
            profiles.Add("joey", "91");
            profiles.Add("mei", "99");
        }

        public static string GetPassword(string key)
        {
            return profiles[key];
        }
    }

    public interface IRsaToken
    {
        string GetRandom(string account);
    }

    public class RsaTokenDao : IRsaToken
    {
        public string GetRandom(string account)
        {
            var seed = new Random((int)DateTime.Now.Ticks & 0x0000FFFF);
            var result = seed.Next(0, 999999).ToString("000000");
            Console.WriteLine("randomCode:{0}", result);

            return result;
        }
    }
}

using System;

using System.Collections.Generic;

namespace RsaSecureToken

{

public class AuthenticationService

{

private IProfile _profileDao;

private IRsaToken _rsaToken;

public AuthenticationService()

{

_profileDao = new ProfileDao();

_rsaToken = new RsaTokenDao();

}

//for test

public AuthenticationService(IProfile profile, IRsaToken rsaToken)

{

_profileDao = profile;

_rsaToken = rsaToken;

}

public bool IsValid(string account, string password)

{

// 根據 account 取得自訂密碼

var passwordFromDao = _profileDao.GetPassword(account);

// 根據 account 取得 RSA token 目前的亂數

var randomCode = _rsaToken.GetRandom(account);

// 驗證傳入的 password 是否等於自訂密碼 + RSA token亂數

var validPassword = passwordFromDao + randomCode;

var isValid = password == validPassword;

if (isValid)

{

return true;

}

else

{

return false;

}

public interface IProfile

{

string GetPassword(string account);

}

public class ProfileDao : IProfile

{

public string GetPassword(string account)

{

return Context.GetPassword(account);

}

public static class Context

{

public static Dictionary<string, string> profiles;

static Context()

{

profiles = new Dictionary<string, string>();

profiles.Add("joey", "91");

profiles.Add("mei", "99");

}

public static string GetPassword(string key)

{

return profiles[key];

}

public interface IRsaToken

{

string GetRandom(string account);

}

public class RsaTokenDao : IRsaToken

{

public string GetRandom(string account)

{

var seed = new Random((int)DateTime.Now.Ticks & 0x0000FFFF);

var result = seed.Next(0, 999999).ToString("000000");

Console.WriteLine("randomCode:{0}", result);

return result;

}

Claire's Blog

單元測試 – 使用Fake Object

抽取相依的物件並且覆寫

如何對現行沒有測試的PROD CODE加上unit test

使用依賴注入

用Fake Object來取代相依物件的方法

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