'If not provided with the right info, should fail.'

def test_failure(self):

    ret = self.call(CmdDummy(), '5')
    lines = ret.splitlines()
    self.assertTrue(any((l.startswith('usage:') for l in lines)))
    self.assertTrue(any((l.startswith('dummy:    error:') for l in lines)))
    ret = self.call(CmdDummy(), 'five    ten')
    lines = ret.splitlines()
    self.assertTrue(any((l.startswith('usage:') for l in lines)))
    self.assertTrue(any((l.startswith('dummy:    error:') for l in lines)))
