在软件开发领域中工作的任何人都将需要在旧代码中添加功能，这些功能可能是从先前的团队继承而来的，您需要对其进行紧急修复。

可以在文献中找到许多遗留代码的定义，我更喜欢的定义是：“通过遗留代码，我们指的是我们害怕改变的有利可图的代码”。

该定义包含两个基本概念：

1.该代码必须有利可图。如果不是这样，我们将无意对其进行更改。2.它必须引起对修改它的恐惧，因为我们可以引入新的bug或依赖影子的东西。

在以下情况下，更容易出错：

•测试未涵盖该代码。•代码不干净；不遵守单一责任原则。•该代码的设计不正确，或者随着时间的流逝其结构变得不合理：对一段代码进行更改可能会产生一些副作用。•您没有时间全面了解正在修改的内容。

测试是我们作为开发人员可用的强大武器。这些测试为我们提供了结果的安全性，并且是一种快速检测错误的方法。但是，我们如何测试未知的代码？构建单元测试套件将为我们提供有关该项目的深入知识，但它将使长时间保持高成本。如果我们无法测试细节，则可以使用Characterization Test，它是描述软件行为的测试。

在这种情况下起重要作用的模式是“ 黄金大师模式”。基本思想很简单：如果我们无法深入了解，我们需要一些有关整个执行过程的指标。我们捕获正确执行的输出（stdout，图像，日志文件等），这就是我们的Golden Master，可用于预期输出。如果当前执行的输出匹配，我们可以确信我们的更改没有引入新的错误。

为了展示Golden Master Pattern的用法，让我们从一个示例开始（完整的代码可以在此处^[1]找到）。我们公司开发了用于命令行的游戏，包括井字游戏（该游戏的实现从此处获取^[2]），我们的老板要求我们更改游戏以提供调整游戏板尺寸的能力。让我们看一下代码：

namespace Tris
{public class Game{//making array and   //by default I am providing 0-9 where no use of zero  static char[] arr = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };static int player = 1; //By default player 1 is set  static int choice; //This holds the choice at which position user want to mark   // The flag variable checks who has won if its value is 1 then someone has won the match if -1 then Match has Draw if 0 then match is still running  static int flag = 0;public static void run(){do{Console.Clear();// whenever loop will be again start then screen will be clear  Console.WriteLine("Player1:X and Player2:O");Console.WriteLine("\n");if (player % 2 == 0)//checking the chance of the player  {Console.WriteLine("Player 2 Chance");}else{Console.WriteLine("Player 1 Chance");}Console.WriteLine("\n");Board();// calling the board Function  choice = int.Parse(Console.ReadLine());//Taking users choice   // checking that position where user want to run is marked (with X or O) or not  if (arr[choice] != 'X' && arr[choice] != 'O'){if (player % 2 == 0) //if chance is of player 2 then mark O else mark X  {arr[choice] = 'O';player++;}else{arr[choice] = 'X';player++;}}else //If there is any position where user wants to run and that is already marked then show message and load board again  {Console.WriteLine("Sorry the row {0} is already marked with {1}", choice, arr[choice]);Console.WriteLine("\n");Console.WriteLine("Please wait 2 second board is loading again.....");Thread.Sleep(2000);}flag = CheckWin();// calling of check win  } while (flag != 1 && flag != -1);// This loof will be run until all cell of the grid is not marked with X and O or some player is not winner Console.Clear();// clearing the console  Board();// getting filled board again  if (flag == 1)// if flag value is 1 then someone has win or means who played marked last time which has win  {Console.WriteLine("Player {0} has won", (player % 2) + 1);}else// if flag value is -1 the match will be drawn and no one is the winner  {Console.WriteLine("Draw");}Console.ReadLine();}// Board method which creats board  private static void Board(){Console.WriteLine("     |     |      ");Console.WriteLine("  {0}  |  {1}  |  {2}", arr[1], arr[2], arr[3]);Console.WriteLine("_____|_____|_____ ");Console.WriteLine("     |     |      ");Console.WriteLine("  {0}  |  {1}  |  {2}", arr[4], arr[5], arr[6]);Console.WriteLine("_____|_____|_____ ");Console.WriteLine("     |     |      ");Console.WriteLine("  {0}  |  {1}  |  {2}", arr[7], arr[8], arr[9]);Console.WriteLine("     |     |      ");}private static int CheckWin(){#region Horzontal Winning Condtion//Winning Condition For First Row   if (arr[1] == arr[2] && arr[2] == arr[3]){return 1;}//Winning Condition For Second Row   else if (arr[4] == arr[5] && arr[5] == arr[6]){return 1;}//Winning Condition For Third Row   else if (arr[6] == arr[7] && arr[7] == arr[8]){return 1;}#endregion#region vertical Winning Condtion//Winning Condition For First Column       else if (arr[1] == arr[4] && arr[4] == arr[7]){return 1;}//Winning Condition For Second Column  else if (arr[2] == arr[5] && arr[5] == arr[8]){return 1;}//Winning Condition For Third Column  else if (arr[3] == arr[6] && arr[6] == arr[9]){return 1;}#endregion#region Diagonal Winning Conditionelse if (arr[1] == arr[5] && arr[5] == arr[9]){return 1;}else if (arr[3] == arr[5] && arr[5] == arr[7]){return 1;}#endregion#region Checking For Draw// If all the cells or values filled with X or O then any player has won the match  else if (arr[1] != '1' && arr[2] != '2' && arr[3] != '3' && arr[4] != '4' && arr[5] != '5' && arr[6] != '6' && arr[7] != '7' && arr[8] != '8' && arr[9] != '9'){return -1;}#endregionelse{return 0;}}}
}

快速阅读后，代码看上去很混乱，职责没有正确分开，变量名也没有意义。

经过准确的阅读后，我们可以找到游戏板，该游戏板存储在“ static char [] arr”中。向阵列添加新元素没有任何效果，因为该阵列直接在PrintBoard和CheckWin函数中访问。现在我们知道要调整游戏板的大小，必须更改大部分代码。

创建一个新项目并运行游戏：

class Program
{static void Main(string[] args){Game.run();}
}

一旦我们印刷了棋盘，游戏就会要求用户输入。我们可以通过从文件中读取输入来实现自动化。

class Program
{private const string InputPath = "input.txt";public static void Main(string[] args){var input = new StreamReader(new FileStream(InputPath, FileMode.Open));Console.SetIn(input);Game.run();input.Close();}
}

所有输入的集合太大，无法使用蛮力测试。我们可以做的就是对输入进行采样。为此，我们考虑井字游戏的最终得分：

•玩家1获胜•玩家2获胜•绘制图形

选择覆盖这三种情况的最低限度的测试集，在文本文件中编写路径，并在golendenMaster文件夹中收集结果：

class Program
{private const string InputFolderPath = "input/";private const string OutputFolderPath = "goldenMaster/";public static void Main(string[] args){int i = 1;foreach (var filePath in Directory.GetFiles(InputFolderPath)) {var input = new StreamReader(new FileStream(filePath, FileMode.Open));var output = new StreamWriter(new FileStream(OutputFolderPath + "output" + i.ToString() + ".txt" , FileMode.CreateNew));Console.SetIn(input);Console.SetOut(output);Game.run();input.Close();output.Close();i++;}}
}

这三个结果文件代表了我们的Golden Master，我们可以在此基础上进行一些特性测试：

[Test]
public void WinPlayerOne()
{inputPath = InputFolderPath + "input1.txt";outputPath = OutputFolderPath + "output.txt";var goldenMasterOutput = GoldenMasterOutput + "output1.txt";var input = new StreamReader(new FileStream(inputPath, FileMode.Open));var output = new StreamWriter(new FileStream(outputPath, FileMode.CreateNew));Console.SetIn(input);Console.SetOut(output);Game.run();input.Close();output.Close();Assert.True(AreFileEquals(goldenMasterOutput, outputPath));
}private bool AreFileEquals(string expectedPath, string actualPath)
{byte[] bytes1 = Encoding.Convert(Encoding.ASCII, Encoding.ASCII, Encoding.ASCII.GetBytes(File.ReadAllText(expectedPath)));byte[] bytes2 = Encoding.Convert(Encoding.ASCII, Encoding.ASCII, Encoding.ASCII.GetBytes(File.ReadAllText(actualPath)));return bytes1.SequenceEqual(bytes2);
}

只要测试是绿色的，我们就可以重构而不必担心破坏某些东西。一种可能的结果可能是：

public static void run()
{char[] board = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };int actualPlayer = 1;while (CheckWin(board) == 0){PrintPlayerChoise(actualPlayer);PrintBoard(board);var choice = ReadPlayerChoise();if (isBoardCellAlreadyTaken(board[choice])){PrintCellIsAlreadyMarketMessage(board[choice], choice);continue;}board[choice] = GetPlayerMarker(actualPlayer);actualPlayer = UpdatePlayer(actualPlayer);}PrintResult(board, actualPlayer);
}

从这段代码中可以看出Board的概念及其职责。让我们尝试在新的Board类中提取行为。新Board应能够：

•印刷板•标记玩家的选择•检查是否有赢家

使用TDD（更多详情，请阅读这篇文章^[3]）制定一个可调整大小的Board（发现测试的完整代码在这里^[4]和阶级的一个位置^[5]）。现在尝试将它们插入游戏中，并检查Golden Master是否保持绿色：

private const int Boardsize = 3;public static void run()
{Board board = new Board(Boardsize);int actualPlayer = 1;while (board.CheckWin() == -1){PrintPlayerChoise(actualPlayer);Console.WriteLine(board.Print());var choice = ReadPlayerChoise();if (!board.UpdateBoard(actualPlayer, choice)){PrintCellIsAlreadyMarketMessage(board.GetCellValue(choice), choice);continue;}actualPlayer = UpdatePlayer(actualPlayer);}PrintResult(board, actualPlayer);
}

此时，我们可以恢复标准输入/标准输出并从用户那里读取电路板的尺寸：

class Program
{public static void Main(string[] args){Console.WriteLine("Insert Diagonal dimension of Board: ");var boardSize = int.Parse(Console.ReadLine());Game.run(boardSize);}
}

如您所见，多亏了Golden Master Pattern，我们能够控制遗留代码并进行重构，而无需担心。但是，所有闪闪发光的东西都不是金子：在“噪声输出”的情况下使用Golden Master可能会很困难，“噪声输出”对于执行无用，但会随时间（例如时间戳记，线程名等）而变化。在这种情况下，我们可以过滤输出并仅考虑重要部分。

我希望它在您下次重写旧项目时对您有用：毕竟，我们担心我们的代码失去控制！

References

[1] 此处: https://github.com/ntonjeta/GoldenMasterExample
[2] 此处获取: https://www.c-sharpcorner.com/UploadFile/75a48f/tic-tac-toe-game-in-C-Sharp/
[3] 这篇文章: https://www.blexin.com/en-US/Article/Blog/TDD-the-whole-code-is-guilty-until-proven-innocent-38
[4] 在这里: https://github.com/ntonjeta/GoldenMasterExample/blob/master/test/GoldenMasterExampleTest/BoardShould.cs
[5] 位置: https://github.com/ntonjeta/GoldenMasterExample/blob/master/lib/Game/Board.cs