old_contents: import mock
  import unittest
  
  from mopidy.utils import network
  
  class FormatHostnameTest(unittest.TestCase):
      def setUp(self):
          self.has_ipv6 = network.has_ipv6
  
      def tearDown(self):
          network.has_ipv6 = self.has_ipv6
  
      def test_format_hostname_prefixes_ipv4_addresses_when_ipv6_available(self):
          network.has_ipv6 = True
          self.assertEqual(network.format_hostname('0.0.0.0'), '::ffff:0.0.0.0')
          self.assertEqual(network.format_hostname('1.0.0.1'), '::ffff:1.0.0.1')
  
      def test_format_hostname_does_nothing_when_only_ipv4_available(self):
          network.has_ipv6 = False
          self.assertEquals(network.format_hostname('0.0.0.0'), '0.0.0.0')
  
  class TryIPv6SocketTest(unittest.TestCase):
      @mock.patch('socket.has_ipv6', False)
      def test_system_that_claims_no_ipv6_support(self):
          self.assertFalse(network._try_ipv6_socket())
  
      @mock.patch('socket.has_ipv6', True)
      @mock.patch('socket.socket')
      def test_system_with_broken_ipv6(self, socket_mock):
          socket_mock.side_effect = IOError()
          self.assertFalse(network._try_ipv6_socket())
  
      @mock.patch('socket.has_ipv6', True)
      @mock.patch('socket.socket')
      def test_with_working_ipv6(self, socket_mock):
          socket_mock.return_value = mock.Mock()
          self.assertTrue(network._try_ipv6_socket())
  
new_contents: import mock
  import unittest
  
  from mopidy.utils import network
  
  class FormatHostnameTest(unittest.TestCase):
      @mock.patch('mopidy.utils.network.has_ipv6', True)
      def test_format_hostname_prefixes_ipv4_addresses_when_ipv6_available(self):
          network.has_ipv6 = True
          self.assertEqual(network.format_hostname('0.0.0.0'), '::ffff:0.0.0.0')
          self.assertEqual(network.format_hostname('1.0.0.1'), '::ffff:1.0.0.1')
  
      @mock.patch('mopidy.utils.network.has_ipv6', False)
      def test_format_hostname_does_nothing_when_only_ipv4_available(self):
          network.has_ipv6 = False
          self.assertEquals(network.format_hostname('0.0.0.0'), '0.0.0.0')
  
  class TryIPv6SocketTest(unittest.TestCase):
      @mock.patch('socket.has_ipv6', False)
      def test_system_that_claims_no_ipv6_support(self):
          self.assertFalse(network._try_ipv6_socket())
  
      @mock.patch('socket.has_ipv6', True)
      @mock.patch('socket.socket')
      def test_system_with_broken_ipv6(self, socket_mock):
          socket_mock.side_effect = IOError()
          self.assertFalse(network._try_ipv6_socket())
  
      @mock.patch('socket.has_ipv6', True)
      @mock.patch('socket.socket')
      def test_with_working_ipv6(self, socket_mock):
          socket_mock.return_value = mock.Mock()
          self.assertTrue(network._try_ipv6_socket())
  
subject: Use mocking for network.has_ipv6 monkey patching