docstr: AlertPublisher - AlertPublisherRepository - all_publishers()
docstr_tok: ["AlertPublisher","-","AlertPublisherRepository","-","all_publishers","(",")"]
code: def test_registers_default_publishers():
      """AlertPublisher - AlertPublisherRepository - all_publishers()"""
      publishers = AlertPublisherRepository.all_publishers()
  
      assert_true(len(publishers) > 0)
  
imports: from mock import patch
  from nose.tools import assert_true, assert_equal, assert_false
  from streamalert.alert_processor.helpers import _assemble_alert_publisher_for_output
  from streamalert.shared.publisher import AlertPublisherRepository, AlertPublisher, CompositePublisher, DefaultPublisher, Register, WrappedFunctionPublisher
  from tests.unit.streamalert.alert_processor.helpers import get_alert
label_desc: Use image node_id 6 for calling the TestAlertPublisherRepository obj's underlying member method code with example usage: obj.test_registers_default_publishers() without return types