I've just realized that unittest doesn't provide a way to test arguments of exception thrown during assertRaises check.

What about this:

>>> class MyTestCase(TestCase):
...     def test_foo(self):
...             with self.assertRaises(SyntaxError) as cm:
...                     compile('asdf jkl', 'file.py', 'eval')
...             self.assertEqual('file.py', cm.exception.filename)

This isn't good enough?

Looks like a hack (and not the obvious one). I guess no asserts return values like this, so that usage is not really intuitive for me.

I found that successful assert in twisted returns exception object. But thanks for workaround anyway.

Using assertRaises as a context manager is not a hack, and is the correct way to do this in unittest.

See also #6275.

I've also found #9587. Now I wonder how many people requested return vs context, and how many would vote for one vs another. Nothing personal - just a pure curiosity.

That was a design decision made by Guido (iirc), and even if it might seem not obvious at first, it's probably just because not everyone is Dutch.
Many people would probably vote on sequence.join(sep) too, but it's unlikely that another way to do it will be introduced.

The doc for assertRaises[0] also is quite clear and even includes an example where the exception args are checked.

[0]: http://docs.python.org/py3k/library/unittest.html#unittest.TestCase.assertRaises

Thanks for clarification, Ezio. I am still using Python 2.7 - that's why I've missed this part.