def METHOD_NAME(self, test, vcn, with_or_without_compartment):
    """
    test adding defined_tags tag to vcn
    """
    vcn_ocid = self._get_vcn_details(vcn)
    session_factory = test.oci_session_factory()
    policy = test.load_policy(
        {
            "name": "add-defined-tag-to-vcn",
            "resource": "oci.vcn",
            "filters": [
                {"type": "value", "key": "id", "value": vcn_ocid},
            ],
            "actions": [{"type": "update", "defined_tags": self.get_defined_tag("add_tag")}],
        },
        session_factory=session_factory,
    )
    policy.run()
    resource = self._fetch_instance_validation_data(policy.resource_manager, vcn_ocid)
    test.assertEqual(resource["id"], vcn_ocid)
    test.assertEqual(self.get_defined_tag_value(resource["defined_tags"]), "true")