old_contents: from unittest import TestCase
  
  from mock import patch
  
  from aws_stager import fetch_candidate
  
  
  class AwsStagerTests(TestCase):
  
      def setUp(self):
          self.print_patcher = patch("aws_stager.candidates.print", create=True)
          self.print_patcher.start()
  
      def tearDown(self):
          self.print_patcher.stop()
  
      @patch("aws_stager.connect_to_region")
      def test_should_connect_to_given_region(self, connect_to_region):
          fetch_candidate("any-aws-region", "any-tag-name")
  
          connect_to_region.assert_called_with("any-aws-region")
  
new_contents: from unittest import TestCase
  
  from mock import patch, Mock
  
  from aws_stager import fetch_candidate
  
  
  class AwsStagerTests(TestCase):
  
      def setUp(self):
          self.print_patcher = patch("aws_stager.candidates.print", create=True)
          self.print_patcher.start()
  
      def tearDown(self):
          self.print_patcher.stop()
  
      @patch("aws_stager.connect_to_region")
      def test_should_connect_to_given_region(self, connect_to_region):
          fetch_candidate("any-aws-region", "any-tag-name")
  
          connect_to_region.assert_called_with("any-aws-region")
  
      @patch("aws_stager.connect_to_region")
      def test_should_fetch_all_potential_candidates(self, connect_to_region):
          fetch_candidate("any-aws-region", "any-tag-name")
  
          connection = connect_to_region.return_value
          connection.get_all_tags.assert_called_with(
              filters={
                  'resource-type': 'image',
                  'value': 'any-tag-name',
                  'key': 'aws-staging-mark'
              })
  
      @patch("aws_stager.CandidateChooser")
      @patch("aws_stager.connect_to_region")
      def test_should_choose_from_candidates(self, connect_to_region, candidate_chooser):
          connection = connect_to_region.return_value
          candidate_tag = Mock(res_id="any-ami-id")
          connection.get_all_tags.return_value = [candidate_tag]
  
          fetch_candidate("any-aws-region", "any-tag-name")
  
          candidate_chooser.assert_called_with([candidate_tag], "any-tag-name")
  
subject: add missing tests