testcase for IS-IS neighbor holdtime (sonic-net#7460)

Testcase to verify IS-IS neighbor hold time.

tests/wan/isis/test_isis_holdtime.py

@@ -0,0 +1,58 @@
+import pytest
+import logging
+
+from tests.common.utilities import wait_until
+from tests.common.helpers.assertions import pytest_assert
+from isis_helpers import DEFAULT_ISIS_INSTANCE as isis_instance
+from isis_helpers import get_nbr_name
+
+
+logger = logging.getLogger(__name__)
+
+
+pytestmark = [
+    pytest.mark.topology('wan-com'),
+]
+
+
+def disable_neighbor_isis(nbr_host, interface_name):
+    out = nbr_host.eos_config(
+                              lines=['no isis enable'],
+                              parents=['interface {}'.format(interface_name)])
+    logging.info('Disable neighbor isis config')
+    return out
+
+
+def check_isis_neighbor(duthost, nbr_name, state):
+    isis_facts = duthost.isis_facts()["ansible_facts"]['isis_facts']
+    if isis_instance not in isis_facts['neighbors']:
+        logger.info("Failed to isis instance {} in dut {}.".format(isis_instance, duthost.hostname))
+        return False
+
+    if state == 'Up' and nbr_name not in isis_facts['neighbors'][isis_instance]:
+        return False
+
+    if state == 'Up' and isis_facts['neighbors'][isis_instance][nbr_name]['state'] == 'Up':
+        return True
+
+    if state == 'Down' and nbr_name not in isis_facts['neighbors'][isis_instance]:
+        return True
+
+    logger.info("Failed to nbr {} in dut {}.".format(nbr_name, duthost.hostname))
+    return False
+
+
+# IS-IS neighbor default IS-IS interval is 10s and multiplier is 3
+def test_isis_holdtime(isis_common_setup_teardown, nbrhosts):
+    selected_connections = isis_common_setup_teardown
+    (dut_host, dut_port, nbr_host, nbr_port) = selected_connections[0]
+
+    nbr_name = get_nbr_name(nbrhosts, nbr_host)
+    pytest_assert(wait_until(10, 2, 0, check_isis_neighbor, dut_host, nbr_name, 'Up'),
+                  "ISIS Neighbor {} is not Up state".format(nbr_name))
+
+    # Disable IS-IS config under PortChannel in neighbor device
+    disable_neighbor_isis(nbr_host, nbr_port)
+
+    pytest_assert(wait_until(30, 2, 1, check_isis_neighbor, dut_host, nbr_name, 'Down'),
+                  "ISIS Neighbor {} is not Down state".format(nbr_name))