old_contents: # Copyright 2019 The gRPC Authors
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """Tests for an actual dns resolution."""
  
  import logging
  import unittest
  
  import grpc
  import six
  
  from tests.unit import test_common
  from tests.unit.framework.common import test_constants
  
  _METHOD = '/ANY/METHOD'
  _REQUEST = b'\x00\x00\x00'
  _RESPONSE = _REQUEST
  
  
  class GenericHandler(grpc.GenericRpcHandler):
  
      def service(self, unused_handler_details):
          return grpc.unary_unary_rpc_method_handler(
              lambda request, unused_context: request,
          )
  
  
  class DNSResolverTest(unittest.TestCase):
  
      def setUp(self):
          self._server = test_common.test_server()
          self._server.add_generic_rpc_handlers((GenericHandler(),))
          self._port = self._server.add_insecure_port('[::]:0')
          self._server.start()
  
      def tearDown(self):
          self._server.stop(None)
  
      def test_connect_loopback(self):
          # NOTE(https://github.com/grpc/grpc/issues/18422)
          # In short, Gevent + C-Ares = Segfault. The C-Ares driver is not
          # supported by custom io manager like "gevent"
          with grpc.insecure_channel('loopback4.unittest.grpc.io:%d' %
                                     self._port) as channel:
              self.assertEqual(
                  channel.unary_unary(_METHOD)(
                      _REQUEST,
                      timeout=test_constants.SHORT_TIMEOUT,
                  ), _RESPONSE)
  
  
  if __name__ == '__main__':
      logging.basicConfig()
      unittest.main(verbosity=2)
  
new_contents: # Copyright 2019 The gRPC Authors
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """Tests for an actual dns resolution."""
  
  import logging
  import unittest
  
  import grpc
  import six
  
  from tests.unit import test_common
  from tests.unit.framework.common import test_constants
  
  _METHOD = '/ANY/METHOD'
  _REQUEST = b'\x00\x00\x00'
  _RESPONSE = _REQUEST
  
  
  class GenericHandler(grpc.GenericRpcHandler):
  
      def service(self, unused_handler_details):
          return grpc.unary_unary_rpc_method_handler(
              lambda request, unused_context: request,
          )
  
  
  class DNSResolverTest(unittest.TestCase):
  
      def setUp(self):
          self._server = test_common.test_server()
          self._server.add_generic_rpc_handlers((GenericHandler(),))
          self._port = self._server.add_insecure_port('[::]:0')
          self._server.start()
  
      def tearDown(self):
          self._server.stop(None)
  
      def test_connect_loopback(self):
          # NOTE(https://github.com/grpc/grpc/issues/18422)
          # In short, Gevent + C-Ares = Segfault. The C-Ares driver is not
          # supported by custom io manager like "gevent"
          # NOTE(b/201064791): use loopback46.unittest.grpc.io since
          # it returns the expected responses even when DNS64 dns servers
          # are used on the test worker (and for purposes of this
          # test the use of loopback4 vs loopback46 makes no difference).
          with grpc.insecure_channel('loopback46.unittest.grpc.io:%d' %
                                     self._port) as channel:
              self.assertEqual(
                  channel.unary_unary(_METHOD)(
                      _REQUEST,
                      timeout=test_constants.SHORT_TIMEOUT,
                  ), _RESPONSE)
  
  
  if __name__ == '__main__':
      logging.basicConfig()
      unittest.main(verbosity=2)
  
subject: fix python dns resolver tests on kokoro MacService (#28344)