使用 Mockito 如何确保在方法中抛出异常

Question

I am using Mockit. I have a situation in which a method throws an exception, catches the exception and logs the exception (and without re-throwing).

Class Test {

       public void abc() {

            try {
                  xyz();
            } catch (Exception e) {
                  LOGGER.error("Exception thrown {} ", e);
            }
       } 

      private void xyz() {
         // Can throw  exception 
         // which goes to the 
         // callee   
      }
}

Now, for some scenarios xyz() can throw exception and which is caught in abc(). It is this scenario I want to test. I can't use @Test(Expected=SomeException.class) as the exception is being caught and logged. However, my test case should look if this exception thrown.

I did search online, however didn't find anything relevant.

Any pointer in how to approach would be helpful.

I referred to this SO question , which seems similar , but isn't what I am looking for.

Answer 1

IMO, Basically you have two options:

1. Mock the logger (do whatever you need for this - refactoring, powermock, etc) this was already described in comments. Other than stating (based on my personal experience ) that usually usage of PowerMock is discouraged I can't really add much to it.

2. Use a "creative" workaround: Add an artificial appender to the logger associated with the class programmatically from within the test. The appender is a "special" one that would store the logging event and will provide an access to it for verification:

// pseudo code that might vary depending on the actual logging framework of your choice
class MyTestAppender extends Appender {
     private LoggingEvent evt = null;
     public void doAppend(LoggingEvent evt) {
       this.evt = evt; 
     }
     public LoggingEvent getEvent() {
       return this.evt;
     }
}

// in test:

@Test
void test() {
    Logger logger = LoggerFactory.getLogger(ClassUnderTest.class);
    MyTestAppender myTestAppender = new MyTestAppender();
    logger.addAppender(myTestAppender);

    classUnderTest.doStuff();
    // now you can verify whether the event has been logged (and stored by the appender):

    LoggingEvent evt = myTestAppender.getEvent();
    assertNotNull(evt); // cool, something was really logged, lets see what:
    assertThat( // verify message, cause exception, whatever you want here
}