def METHOD_NAME(self, handler_cisco):
    # get hold of the read-only Snmp-object
    snmp_read_only_handler = handler_cisco._get_read_only_handle()
    # replace get-method on Snmp-object with a mock-method
    # this get-method returns a vlan-number
    snmp_read_only_handler.get = Mock(return_value=77)
    ifc = Mock(ifindex=1)
    assert handler_cisco.get_interface_native_vlan(ifc) == 77, "getVlan-test failed"
    snmp_read_only_handler.get.assert_called_with('1.3.6.1.4.1.9.9.68.1.2.2.1.2.1')