Test TX drop counter on oper down

tests/portstat/test_drop_counters_on_down_intf.py

@@ -0,0 +1,60 @@
+import logging
+import pytest
+import time
+
+from tests.common.helpers.assertions import pytest_assert
+from tests.common.portstat_utilities import parse_portstat
+
+logger = logging.getLogger('__name__')
+
+pytestmark = [
+    pytest.mark.topology('any')
+]
+
+
+def test_tx_drop_counters_on_oper_down_intf(duthosts, enum_rand_one_per_hwsku_frontend_hostname, nbrhosts):
+    """
+    Test that TX_DROP counters are not incremented when the interface is oper down.
+    """
+    duthost = duthosts[enum_rand_one_per_hwsku_frontend_hostname]
+    interfaces = duthost.shell("show lldp table")['stdout_lines'][3:]
+    # find an oper up and admin up interface
+    if len(interfaces) == 0:
+        pytest.skip('No interfaces connected to switch neighbors found')
+    intf = interfaces[0].split()[0]
+    neighbor = interfaces[0].split()[1]
+    neighbor_intf = interfaces[0].split()[2]
+
+    assert neighbor, "Cannot find the hostname of neighbor connected to {}".format(intf)
+    assert neighbor_intf, "Cannot find the interface name of neighbor connected to {}".format(intf)
+
+    # get the neighbor's IP
+    bgp_neighbors = duthost.shell("show ip bgp summary")['stdout_lines']
+    for line in bgp_neighbors:
+        if neighbor in line:
+            neighbor_ip = line.split()[0]
+            break
+    assert neighbor_ip, "Cannot find the IP address of neighbor"
+
+    logger.info('DUT Interface: {}, Neighbor: {}, Neighbor Interface: {}, Neighbor IP: {}'
+                .format(intf, neighbor, neighbor_intf, neighbor_ip))
+
+    # shutdown the interface of neighbor
+    nbrhosts[neighbor]['host'].shutdown(neighbor_intf)
+    time.sleep(2)
+
+    # collect portstat before sleeping
+    before_portstat = parse_portstat(duthost.command('portstat -i {}'.format(intf))['stdout_lines'])
+
+    # Ping the neighbor from DUT
+    duthost.command('ping {} -c 10'.format(neighbor_ip), module_ignore_errors=True)
+
+    # collect portstat after sleeping
+    after_portstat = parse_portstat(duthost.command('portstat -i {}'.format(intf))['stdout_lines'])
+
+    # Assert that TX_DROP counters are not incremented
+    pytest_assert(before_portstat[intf]['tx_drp'] == after_portstat[intf]['tx_drp'],
+                  'TX_DROP counters should not be incremented when the interface is administratively down')
+
+    # recover the neighbor interface
+    nbrhosts[neighbor]['host'].no_shutdown(neighbor_intf)