tests: better reporting for unexpected packets

Raise a new UnexpectedPacketErrror, when a packet is captured
unexpectedly. This pretty-prints a terse description of said packet.

Type: improvement
Signed-off-by: Klement Sekera <klement.sekera@gmail.com>
Change-Id: Ibac19fc5bbd82a150fec3c90940a37af6344fd4f

3 files changed, 37 insertions, 22 deletions

diff --git a/test/framework.py b/test/framework.py
index 1c81e8afabc..9266227f18e 100644
--- a/test/framework.py
+++ b/test/framework.py
@@ -1310,8 +1310,7 @@ class VppTestCase(CPUInterface, unittest.TestCase):
             if not timeout:
                 timeout = 1
             for i in self.pg_interfaces:
-                i.get_capture(0, timeout=timeout)
-                i.assert_nothing_captured(remark=remark)
+                i.assert_nothing_captured(timeout=timeout, remark=remark)
                 timeout = 0.1
         finally:
             if trace:
@@ -1365,8 +1364,7 @@ class VppTestCase(CPUInterface, unittest.TestCase):
             timeout = 1
         for i in self.pg_interfaces:
             if i not in outputs:
-                i.get_capture(0, timeout=timeout)
-                i.assert_nothing_captured()
+                i.assert_nothing_captured(timeout=timeout)
                 timeout = 0.1
 
         if stats_diff:
diff --git a/test/util.py b/test/util.py
index 653b667eb6c..2c24571c350 100644
--- a/test/util.py
+++ b/test/util.py
@@ -6,6 +6,7 @@ import socket
 from socket import AF_INET6
 import os.path
 from copy import deepcopy
+from collections import UserDict
 
 import scapy.compat
 from scapy.layers.l2 import Ether
@@ -24,8 +25,12 @@ null_logger = logging.getLogger('VppTestCase.util')
 null_logger.addHandler(logging.NullHandler())
 
 
+def pr(packet):
+    return packet.__repr__()
+
+
 def ppp(headline, packet):
-    """ Return string containing the output of scapy packet.show() call. """
+    """ Return string containing headline and output of scapy packet.show() """
     return '%s\n%s\n\n%s\n' % (headline,
                                hexdump(packet, dump=True),
                                packet.show(dump=True))
@@ -453,6 +458,15 @@ def reassemble4(listoffragments):
     return reassemble4_core(listoffragments, True)
 
 
+class UnexpectedPacketError(Exception):
+    def __init__(self, packet, msg=""):
+        self.packet = packet
+        self.msg = msg
+
+    def __str__(self):
+        return f"\nUnexpected packet:\n{pr(self.packet)}{self.msg}"
+
+
 def recursive_dict_merge(dict_base, dict_update):
     """Recursively merge base dict with update dict, return merged dict"""
     for key in dict_update:
@@ -467,7 +481,7 @@ def recursive_dict_merge(dict_base, dict_update):
     return dict_base
 
 
-class StatsDiff:
+class StatsDiff(UserDict):
     """
     Diff dictionary is a dictionary of dictionaries of interesting stats:
 
@@ -487,14 +501,10 @@ class StatsDiff:
     sw-if-index.
     """
 
-    def __init__(self, stats_diff={}):
-        self.stats_diff = stats_diff
+    __slots__ = ()  # prevent setting properties to act like a dictionary
 
-    def update(self, sw_if_index, key, value):
-        if sw_if_index in self.stats_diff:
-            self.stats_diff[sw_if_index][key] = value
-        else:
-            self.stats_diff[sw_if_index] = {key: value}
+    def __init__(self, data):
+        super().__init__(data)
 
     def __or__(self, other):
-        return recursive_dict_merge(deepcopy(self.stats_diff), other)
+        return recursive_dict_merge(deepcopy(self.data), other)
diff --git a/test/vpp_pg_interface.py b/test/vpp_pg_interface.py
index 01f10fccfc9..434a3005bd7 100644
--- a/test/vpp_pg_interface.py
+++ b/test/vpp_pg_interface.py
@@ -16,7 +16,7 @@ from scapy.layers.l2 import Ether, ARP
 from scapy.layers.inet6 import IPv6, ICMPv6ND_NS, ICMPv6ND_NA,\
     ICMPv6NDOptSrcLLAddr, ICMPv6NDOptDstLLAddr, ICMPv6ND_RA, RouterAlert, \
     IPv6ExtHdrHopByHop
-from util import ppp, ppc
+from util import ppp, ppc, UnexpectedPacketError
 from scapy.utils6 import in6_getnsma, in6_getnsmac, in6_ismaddr
 
 
@@ -287,13 +287,19 @@ class VppPGInterface(VppInterface):
             remaining_time -= elapsed_time
         if capture:
             self.generate_debug_aid("count-mismatch")
+            if len(capture) > 0 and 0 == expected_count:
+                rem = f"\n{remark}" if remark else ""
+                raise UnexpectedPacketError(
+                    capture[0],
+                    f"\n({len(capture)} packets captured in total){rem}")
             raise Exception("Captured packets mismatch, captured %s packets, "
                             "expected %s packets on %s" %
                             (len(capture.res), expected_count, name))
         else:
             raise Exception("No packets captured on %s" % name)
 
-    def assert_nothing_captured(self, remark=None, filter_out_fn=is_ipv6_misc):
+    def assert_nothing_captured(self, timeout=1, remark=None,
+                                filter_out_fn=is_ipv6_misc):
         """ Assert that nothing unfiltered was captured on interface
 
         :param remark: remark printed into debug logs
@@ -303,7 +309,8 @@ class VppPGInterface(VppInterface):
         if os.path.isfile(self.out_path):
             try:
                 capture = self.get_capture(
-                    0, remark=remark, filter_out_fn=filter_out_fn)
+                    0, timeout=timeout, remark=remark,
+                    filter_out_fn=filter_out_fn)
                 if not capture or len(capture.res) == 0:
                     # junk filtered out, we're good
                     return
@@ -311,12 +318,12 @@ class VppPGInterface(VppInterface):
                 pass
             self.generate_debug_aid("empty-assert")
             if remark:
-                raise AssertionError(
-                    "Non-empty capture file present for interface %s (%s)" %
-                    (self.name, remark))
+                raise UnexpectedPacketError(
+                    capture[0],
+                    f" ({len(capture)} packets captured in total) ({remark})")
             else:
-                raise AssertionError("Capture file present for interface %s" %
-                                     self.name)
+                raise UnexpectedPacketError(
+                    capture[0], f" ({len(capture)} packets captured in total)")
 
     def wait_for_pg_stop(self):
         # wait till packet-generator is stopped