Test exceptions are raised and the exception message is correct.

test_exception.py

import unittest


def raise_exception(yup=True):
    if yup:
        raise ValueError('Yup, exception raised.')


class ExceptionMessageTestCase(unittest.TestCase):
    def assertRaisesMessage(self, exception, msg, func, *args, **kwargs):
        try:
            func(*args, **kwargs)
            self.fail()
        except exception as e:
            self.assertEqual(str(e), msg)


class BasicExceptionTest(unittest.TestCase):
    def test_simple(self):
        self.assertRaises(ValueError, raise_exception, True)

    def test_message(self):
        try:
            raise_exception(True)
            self.fail()
        except ValueError as e:
            self.assertEqual(str(e), 'Yup, exception raised.')


class MessageExceptionTest(ExceptionMessageTestCase):
    def test_simple(self):
        self.assertRaises(ValueError, raise_exception, True)

    def test_message(self):
        self.assertRaisesMessage(ValueError, 'Yup, exception raised.',
                                 raise_exception, True)


if __name__ == '__main__':
    unittest.main(verbosity=2)