java - 使用 junit 测试带有 switch case 的程序

Question

我想在 junit 中为计算器程序编写测试用例。我是 junit 环境的新手。我可以为其他程序编写测试，但有点坚持测试 switch() 案例。

我真的很想知道怎么做。

提前致谢

这是我的程序

 import java.util.Scanner;

 //This program performs basic math operations such as :- +,-,*,/
  public class Calculator 

  {      
 public static void main(String[] args) 

 {
     double number1, number2;
     String Mathoperation;
     Scanner scannerObject = new Scanner(System.in);

     System.out.println("Enter first number");
     number1 = scannerObject. nextDouble();

     System.out.println("Enter second number");
     number2 = scannerObject. nextDouble();

     Scanner UserInput = new Scanner(System.in);
     System.out.println("\nHere are your options:");
     System.out.println("\n1. Addition, 2. Subtraction, 3. Divison, 4. Multiplication");
     Mathoperation = UserInput.next();

     switch (Mathoperation)  
     {
       case "1":
       System.out.println("Your answer is " + (number1 + number2));
       break;

       case "2":
       System.out.println("Your answer is " + (number1 - number2));
       break;

       case "3":
       System.out.println("Your answer is " + (number1 / number2));
       break;

       case "4":
       System.out.println("Your asnwer is " + (number1 * number2));
       break;

       default:
       System.out.println("");      
     }   
 }  

}

Answer 1

编写单元测试的第一步是编写可测试的代码。此时你的代码不是很可测试，也就是说你可以测试它但它不会是最好的测试。让我们来看看原因。

第一个原因是您的所有代码都在主函数中。你通常想避免这种情况。这有多种原因，但我认为最大的两个原因是可读性和可重用性。通常你会想把东西放到不同的类中，但为了时间的缘故，我们将简单地将你的数学开关放入它自己的函数中。

import java.util.Scanner;

     //This program performs basic math operations such as :- +,-,*,/
public class Calculator 

{      
 public static void main(String[] args) 

 {
   double number1, number2;
   String Mathoperation;
   Scanner scannerObject = new Scanner(System.in);

   System.out.println("Enter first number");
   number1 = scannerObject. nextDouble();

   System.out.println("Enter second number");
   number2 = scannerObject. nextDouble();

   Scanner UserInput = new Scanner(System.in);
   System.out.println("\nHere are your options:");
   System.out.println("\n1. Addition, 2. Subtraction, 3. Divison, 4. Multiplication");
   Mathoperation = UserInput.next();
   doMath(Mathoperation, number1, number2)
 }

 public double doMath(String Mathoperation, double number1, double number2){
   switch (Mathoperation)  
   {
     case "1":
     System.out.println("Your answer is " + (number1 + number2));
     break;

     case "2":
     System.out.println("Your answer is " + (number1 - number2));
     break;

     case "3":
     System.out.println("Your answer is " + (number1 / number2));
     break;

     case "4":
     System.out.println("Your asnwer is " + (number1 * number2));
     break;

     default:
     System.out.println("");      
   }   
 }
}

好的，现在我们有了自己的数学运算方法。一个问题。这本身不是一个单元，这实际上是加法和我们的数学运算之间的集成。这意味着，为了进行测试，我们需要测试每个算术组合(加、减、除、乘)，以及该方法是否选择了正确的运算符。那比我们想要的要多得多，而且不是一个很好的测试，那么我们如何解决这个问题呢？很简单，我们进一步分解

import java.util.Scanner;

     //This program performs basic math operations such as :- +,-,*,/
public class Calculator {
//Code for use input somewhere here      
 public double doMath(String Mathoperation, double number1, double number2){
   switch (Mathoperation)  
   {
     case "1":
     System.out.println("Your answer is " + add(number1, number2));
     break;

     case "2":
     System.out.println("Your answer is " + sub(number1, number2));
     break;

     case "3":
     System.out.println("Your answer is " + div(number1, number2));
     break;

     case "4":
     System.out.println("Your answer is " + mul(number1, number2));
     break;

     default:
     System.out.println("");      
   }   
 }
 public double add(double number1, double number2){
   return number1 + number2;
 }
 public double sub(double number1, double number2){
   return number1 - number2;
 }
 public double mul(double number1, double number2){
   return number1 * number2;
 }
 public double div(double number1, double number2){
   return number1 / number2;
 }
}

现在我们的单位更容易分解。您可以从这里为您的 add、sub、div 和 mul 函数编写测试。很好地测试这些以确保它们按预期运行。然后为 doMath 函数编写测试以确保它将值传递给正确的操作。通过这种方式，当出现故障时，您可以确切地知道它的故障位置和问题所在，而不必猜测。您会知道 doMath 是否有问题，或者您的其他数学方法是否有问题。它还允许您更轻松地将您的方法重用于其他事情，所以双赢