'Test that calls can be scheduled for later with the fake clock and
hands back an L{IDelayedCall}.'

def testCallLater(self):

    c = task.Clock()
    call = c.callLater(1, (lambda a, b: None), 1, b=2)
    self.assertTrue(interfaces.IDelayedCall.providedBy(call))
    self.assertEqual(call.getTime(), 1)
    self.assertTrue(call.active())
