Checking for 2 expected values in Junit

Question

I have a java program which throws an exception with 2 different messages for 2 different scenarios and I want the Junit test case to check for equality for both of these messages. As an example -

public void amethod() {
           // do some processing
        if(scenario1 == true) {
            throw new MySystemException("An error occured due to case 1 being incorrect.");
        }
        else if(scenario2 == true) {
            throw new MySystemException("An error occured as case 2 could not be found");
        }
    }  

Now the JUnit for this would be something like-

public void testAMethod() {
    // do something
    assertEquals("Expected", "Actual");
}

As I understand, in this above example, if I use the Scenario1 exception message the junit will fail when an exception is thrown for Scenario2 and vice versa.
I would like to know if there is any other way provided in Junit by which I can use this one test method and check for both the messages for the test to pass?
Something like an OR, if possible to provide the "Expected" value with both these expected message.
I hope my query is clear enough.

Thanks

UPDATE

Sorry for the delayed response, had got caught up with some other urgent matter.
Thank you all for the very nice suggestions, it certainly has helped me to understand a bit better now.
Eventually, to keep it rather simple I decided to implement a somewhat similar solution suggested by Don Roby. So created a new test class which looks like -

public void testAMethodScenario1() {
    // do the necessary
    assertEquals("Expected Exception Message 1", "Actual");
}

public void testAMethodScenario2() {
    // do the necessary
    assertEquals("Expected Exception Message 2", "Actual");
}  

Thank you all again for your responses.

Answer 1

I think you need to manually catch the exception (for each scenario) and individually check the message:

try {
    // trigger scenario 1
    fail("An exception should have been thrown here !");
} catch (MySystemException e1) {
    assertEquals("Wrong error message", m1, e1.getMessage());
}

try {
    // trigger scenario 2
    fail("An exception should have been thrown here !");
} catch (MySystemException e2) {
    assertEquals("Wrong error message", m2, e2.getMessage());
}

Of course, you can have these scenarios defined as enum constants and simply iterate through them and check each of them within a loop, since the "copy/paste design pattern" is pretty obvious in the above code. :)

Answer 2

You seem to be asking two things here, how to test an exception and how to assert that a value matches either of two possible expected values.

To test for an exception, you can either use a JUnit4 annotation:

@Test(expected=MySystemException.class)
public void testException() {
   amethod();
}

or use a try-catch in your test:

@Test
public void testException() {
   try {
      amethod();
      fail("MySystemException expected");
   }
   catch (MySystemException e) {
      // Success!
   }
}

And if you have only one message, in the try-catch version you can assert that you got it with an AssertEquals in the catch block.

The best testing would have separate tests for your two scenarios, and expect the correct single message. Better code might in fact have distinct exceptions for the two situations.

But the need for a more complex assertion than simple equality does come up anyway, and there's an elegant solution for it in Hamcrest matchers.

Using that for this situation, you could write something like (untested - don't trust my syntax completely):

@Test
public void testException() {
   try {
      amethod();
      fail("MySystemException expected");
   }
   catch (MySystemException e) {
      String expectedMessage1 = "An error occured due to case 1 being incorrect.";
      String expectedMessage2 = "An error occured as case 2 could not be found";
      assertThat(e.getMessage(), 
                 anyOf(equalTo(expectedMessage1), equalTo(expectedMessage2)));
   }
}