JUnit测试除以0算术异常

发表时间：2022-07-30 00:32:57 阅读：285

首先，我对Java相当陌生&我的需求是创建一个方法来划分两个整数，并为此创建一个JUnit测试方法，该方法应该预期零除算术异常.然而，我的测试失败了，出现了一个断言错误，即使测试方法中没有涉及0.我怎样才能解决这个问题？

public class Calculate {

    public static int division(int num1, int num2) throws ArithmeticException {
        try {
            return num1/ num2;
        } catch (ArithmeticException e) {
            throw new ArithmeticException("Cannot divide by 0");
        }
    }

试验方法

@Test (expected = java.lang.ArithmeticException.class)
public void division() {
    int firstNum = 10;
    int secondNum = 2;
    int expected = 5;
    Calculate test = new Calculate();
    int actual = test.division(firstNum, secondNum);
    assertEquals(expected, actual);
}

🎖️ 优质答案

It looks like you are trying to test everything with a single test. Instead, you should write a sepearate test for each scenario:

   // "happy path" that division works correctly
   @Test 
   public void division() {
       int firstNum = 10;
       int secondNum = 2;
       int expected = 5;
       Calculate test = new Calculate();
       int actual = test.division(firstNum, secondNum);
       assertEquals(expected, actual);
   }

   // error path that exception is thrown
   @Test (expected = java.lang.ArithmeticException.class)
   public void divisionByZero() {
       int firstNum = 10;
       int secondNum = 0;
       Calculate test = new Calculate();
       int actual = test.division(firstNum, secondNum);
   }

@Test(expected = ...) only works with JUnit 4. It's better to use assertThrows. This was added in JUnit 5 and backported to JUnit 4.13:

@Test
public void divisionByZero() {
    int firstNum = 10;
    int secondNum = 0;
    Calculate test = new Calculate();
    ArithmeticException thrown = assertThrows(ArithmeticException.class,
            () -> test.division(firstNum, secondNum));
    assertEquals("Cannot divide by 0", thrown.getMessage());
}