Rudimentary Twisted Trial Unit test that hangs

test_rudementary.py

from twisted.trial import unittest
from twisted.internet.defer import Deferred


class TestRudimentary(unittest.TestCase):

    # This test case succeeds, but hangs at the end of the invocation when running through nosetests. 
    # How can this be fixed?
    def test_rudimentary(self):
        def done(_ignored):
            print "DONE"

        defer = Deferred()
        defer.addCallback(done)
        return defer