无法使用嘲笑引发异常-未捕获引发的异常 [英] Unable to use mocking to throw an exception - the thrown exception is not being caught

问题描述

我有一个方法可以模拟抛出的异常，以便输入catch语句:

I have a method where I'd like to mock an exception being thrown so that the catch statement is entered:

public static String func(String val) {
  try {
    MessageDigest md5 = MessageDigest.getInstance("MD5");
    return Base64.encode(md5.digest(val.getBytes()));
  } catch (NoSuchAlgorithmException toCatch) {
      return "*";
  }
}

我写的测试是这样的:

@Test
public void testFunc() throws Exception {
  MessageDigest md5 = PowerMockito.mock(MessageDigest.class);
  PowerMockito.when(md5.getInstance(anyString())).thenThrow(new NoSuchAlgorithmException());  
  Assert.assertEquals("*", func("in"));
}

但是我得到了:

java.security.NoSuchAlgorithmException:  MessageDigest not available

PowerMockito.when()行上的

.这意味着异常已通过但未被捕获?我在做什么错了?

on the PowerMockito.when() line. Which implies the exception has been through, but not caught? What am I doing wrong?

更新: 我已经尝试了以下修改

Update: I have tried the following modifications

@PrepareForTest({MessageDigest.class}) 
@Test
public void testFunc() throws Exception {
  PowerMockito.mockStatic(MessageDigest.class); 
  PowerMockito.when(MessageDigest.getInstance(anyString())).thenThrow(new NoSuchAlgorithmException());
  Assert.assertEquals("*", testFunc("in"));
}

这将导致该函数在不触发异常的情况下运行.

This causes the function to run without triggering the exception.

这:

@PrepareForTest({MessageDigest.class})
@Test
public void testFunc() throws Exception { 
  PowerMockito.mockStatic(MessageDigest.class);
  MessageDigest md5 = PowerMockito.mock(MessageDigest.class); 
  PowerMockito.doThrow(new NoSuchAlgorithmException()).when(md5, "getInstance", anyString()); 
  Assert.assertEquals("*", func("in"));
} 

仍然不调用catch语句，类似于我之前获得的内容.

Still doesn't invoke the catch statement, similar to what I was getting before.

推荐答案

由于MessageDigest是Java系统类，因此您需要按照以下方式分别处理它们: https://github.com/powermock/powermock/wiki/Mock-System

As MessageDigest is a Java system class, you need to deal with them differently as per: https://github.com/powermock/powermock/wiki/Mock-System

因此，在@PrepareForTest批注中声明测试类，如下所示: @PrepareForTest({MessageDigest.class, MyTest.class})

So declare the test class in the @PrepareForTest annotation as follows: @PrepareForTest({MessageDigest.class, MyTest.class})

不确定此注释是否按照您的示例作为方法级别使用，但应在类级别使用:

Not sure if this annotation works as method level as per your example, but it should at class level:

@RunWith(PowerMockRunner.class)
@PrepareForTest({MessageDigest.class, MyTest.class})
public class MyTest {

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