def METHOD_NAME(self):
    session_factory = self.replay_flight_data("test_cfn_add_tag")
    p = self.load_policy(
        {
            "name": "cfn-add-tag",
            "resource": "cfn",
            "filters": [{"tag:DesiredTag": "absent"}],
            "actions": [
                {"type": "tag", "key": "DesiredTag", "value": "DesiredValue"}
            ],
        },
        session_factory=session_factory,
    )
    resources = p.run()
    self.assertEqual(len(resources), 1)
    client = session_factory(region="us-east-1").client("cloudformation")
    tags = client.describe_stacks(StackName=resources[0]["StackName"])["Stacks"][0][
        "Tags"
    ]
    self.assertEqual(
        [tags[0]["Key"], tags[0]["Value"]], ["DesiredTag", "DesiredValue"]
    )