text: from celery.tests.utils import unittest
  
  from celery import backends
  from celery.backends.amqp import AMQPBackend
  from celery.backends.cache import CacheBackend
  
  
  class TestBackends(unittest.TestCase):
  
      def test_get_backend_aliases(self):
          expects = [("amqp", AMQPBackend),
                     ("cache", CacheBackend)]
          for expect_name, expect_cls in expects:
              self.assertIsInstance(backends.get_backend_cls(expect_name)(),
                                    expect_cls)
  
      def test_get_backend_cahe(self):
          backends._backend_cache = {}
          backends.get_backend_cls("amqp")
          self.assertIn("amqp", backends._backend_cache)
          amqp_backend = backends.get_backend_cls("amqp")
          self.assertIs(amqp_backend, backends._backend_cache["amqp"])
  