'The result of ``compute_instance_id`` is cached indefinitely.'

def test_compute_instance_id(self):

    initial = self.cache.compute_instance_id()
    later = [self.cache.compute_instance_id() for _ in range(10)]
    self.assertEqual((later, self.counting_proxy.num_calls('compute_instance_id')), (([initial] * 10), 1))
