def METHOD_NAME(core_manager):
    assert not core_manager.core_running
    assert not core_manager.core_started
    assert core_manager.core_started_at is None
    with patch.object(core_manager, 'check_core_api_port') as check_core_api_port:
        core_manager.on_core_started()
        assert check_core_api_port.called