text: #!/usr/bin/env python3
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  #
  
  import unittest
  
  import node
  import config
  import command
  import mle
  
  LEADER = 1
  DUT_ROUTER1 = 2
  ROUTER2 = 3
  ROUTER24 = 24
  
  
  class Cert_5_2_06_RouterDowngrade(unittest.TestCase):
  
      def setUp(self):
          self.simulator = config.create_default_simulator()
  
          self.nodes = {}
          for i in range(1, 25):
              self.nodes[i] = node.Node(i, simulator=self.simulator)
              self.nodes[i].set_panid()
              self.nodes[i].set_mode('rsdn')
              self.nodes[i].set_router_selection_jitter(1)
              if i != DUT_ROUTER1:
                  self.nodes[i].set_router_upgrade_threshold(32)
                  self.nodes[i].set_router_downgrade_threshold(32)
  
      def tearDown(self):
          for n in list(self.nodes.values()):
              n.stop()
              n.destroy()
          self.simulator.stop()
  
      def test(self):
          # 1 Ensure topology is formed correctly without ROUTER24.
          self.nodes[LEADER].start()
          self.simulator.go(5)
          self.assertEqual(self.nodes[LEADER].get_state(), 'leader')
  
          for i in range(2, 24):
              self.nodes[i].start()
              self.simulator.go(5)
              self.assertEqual(self.nodes[i].get_state(), 'router')
  
          # This method flushes the message queue so calling this method again
          # will return only the newly logged messages.
          dut_messages = self.simulator.get_messages_sent_by(DUT_ROUTER1)
  
          # 2 ROUTER24: Attach to network.
          # All reference testbed devices have been configured with downgrade threshold as 32 except DUT_ROUTER1,
          # so we don't need to ensure ROUTER24 has a better link quality on
          # posix.
          self.nodes[ROUTER24].start()
          self.simulator.go(5)
          self.assertEqual(self.nodes[ROUTER24].get_state(), 'router')
  
          # 3 DUT_ROUTER1:
          self.simulator.go(10)
          self.assertEqual(self.nodes[DUT_ROUTER1].get_state(), 'child')
  
          # Verify it sent a Parent Request and Child ID Request.
          dut_messages = self.simulator.get_messages_sent_by(DUT_ROUTER1)
          dut_messages.next_mle_message(mle.CommandType.PARENT_REQUEST)
          dut_messages.next_mle_message(mle.CommandType.CHILD_ID_REQUEST)
  
          # Verify it sent an Address Release Message to the Leader when it
          # attached as a child.
          msg = dut_messages.next_coap_message('0.02')
          command.check_address_release(msg, self.nodes[LEADER])
  
          # 4 & 5
          router1_rloc = self.nodes[DUT_ROUTER1].get_ip6_address(
              config.ADDRESS_TYPE.RLOC)
          self.assertTrue(self.nodes[LEADER].ping(router1_rloc))
  
  
  if __name__ == '__main__':
      unittest.main()
  