Question

I am using unittest to assert that my script raises the right SystemExit code.

Based on the example from http://docs.python.org/3.3/library/unittest.html#unittest.TestCase.assertRaises

with self.assertRaises(SomeException) as cm:
    do_something()

the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)

I coded this:

with self.assertRaises(SystemExit) as cm:
    do_something()

the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)

However, this does not work. The following error comes up:

AttributeError: 'SystemExit' object has no attribute 'error_code'

Answer 1

SystemExit derives directly from BaseException and not StandardError, thus it does not have the attribute error_code.

Instead of error_code you have to use the attribute code. The example would look like this:

with self.assertRaises(SystemExit) as cm:
    do_something()

the_exception = cm.exception
self.assertEqual(the_exception.code, 3)