expected_failure decorator

#!/usr/bin/env python
import unittest

from functools import wraps

def something_that_returns_true():
    return True

def something_else_that_returns_true():
    return False

def something_that_returns_ture():
    # raises NameError!
    return Ture

def something_that_got_fixed():
    # return []
    # ^ empty list is False!
    return [None]

def expected_failure(exc=None.__class__):
    def wrap(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            try:
                rv = f(*args, **kwargs)
            except AssertionError, e:
                return None
            except Exception, e:
                if isinstance(e, exc):
                    rv = None
                else:
                    raise
            else:
                raise AssertionError("%s was expected to fail, but did not" % 
                                     f.__name__)
            return rv
        return wrapper
    return wrap

class TestSomething(unittest.TestCase):

    def test_something_that_works(self):
        self.assert_(something_that_returns_true())

    @expected_failure()
    def test_something_thats_broken(self):
        self.assert_(something_else_that_returns_true())

    @expected_failure(NameError)
    def test_something_thats_way_broken(self):
        self.assert_(something_that_returns_ture())

    # commiter of fix needs to remove this decorator
    @expected_failure()
    def test_something_that_needs_fixing(self):
        self.assert_(something_that_got_fixed())


if __name__ == "__main__":
    unittest.main()