What's the actual use of 'fail' in JUnit test case?

Question

What\'s the actual use of \'fail\' in JUnit test case?

Answer 1

Some cases where I have found it useful:

• mark a test that is incomplete, so it fails and warns you until you can finish it
• making sure an exception is thrown:

try{
  // do stuff...
  fail("Exception not thrown");
}catch(Exception e){
  assertTrue(e.hasSomeFlag());
}

Note:

Since JUnit4, there is a more elegant way to test that an exception is being thrown: Use the annotation @Test(expected=IndexOutOfBoundsException.class)

However, this won't work if you also want to inspect the exception, then you still need fail().

Answer 2

I think the usual use case is to call it when no exception was thrown in a negative test.

Something like the following pseudo-code:

test_addNilThrowsNullPointerException()
{
    try {
        foo.add(NIL);                      // we expect a NullPointerException here
        fail("No NullPointerException");   // cause the test to fail if we reach this            
     } catch (NullNullPointerException e) {
        // OK got the expected exception
    }
}