jUnit same exception in different cases

Question

I'm writing a jUnit test for a constructor that parses a String and then check numerous things. When there's wrong data, for every thing, some IllegalArgumentException with different message is thrown. So I would like to write tests for it, but how can i recognize what error was thrown? This is how can I do it:

@Test(expected=IllegalArgumentException.class)
public void testRodneCisloRok(){
    new RodneCislo("891415",dopocitej("891415"));
}

and this is how I would like to be, but I don't know if it is possible to write it somehow:

@Test(expected=IllegalArgumentException.class("error1"))
public void testRodneCisloRok(){
    new RodneCislo("891415",dopocitej("891415"));
}

Answer 1

If you have JUnit 4.7 or above you can use this (elegant) way:

@Rule
public ExpectedException exception = ExpectedException.none();

@Test
public void testRodneCisloRok(){
    exception.expect(IllegalArgumentException.class);
    exception.expectMessage("error1");
    new RodneCislo("891415",dopocitej("891415"));
}

Answer 2

You'll need to do it the old fashioned way:

@Test
public void testRodneCisloRok() {
    try {
       new RodneCislo("891415",dopocitej("891415"));
       fail("expected an exception");
    } catch (IllegalArgumentException ex) {
       assertEquals("error1", ex.getMessage());
    }
}

The @Test(expected=...) syntax is a handy convenience, but it's too simple in many cases.

If it is important to distinguish between exception conditions, you might want to consider developing a class hierarchy of exceptions, that can be caught specifically. In this case, a subclass of IllegalArgumentException might be a good idea. It's arguably better design, and your test can catch that specific exception type.