Fix spurious test errors in test_ipv6.py (#1072)

tests/scripts/thread-cert/ipv6.py

@@ -27,18 +27,19 @@
 #  POSSIBILITY OF SUCH DAMAGE.
 #
 
-try:
-    from itertools import izip_longest as zip_longest
-except ImportError:
-    from itertools import zip_longest
-
-from ipaddress import ip_address
-
 import abc
 import io
 import struct
 import sys
 
+from binascii import hexlify
+from ipaddress import ip_address
+
+try:
+    from itertools import izip_longest as zip_longest
+except ImportError:
+    from itertools import zip_longest
+
 
 # Next headers for IPv6 protocols
 IPV6_NEXT_HEADER_HOP_BY_HOP = 0
@@ -696,6 +697,9 @@ class HopByHopOptionHeader(ConvertibleToBytes, BuildableFromBytes):
     def __len__(self):
         return self._header_length
 
+    def __repr__(self):
+        return "HopByHopOptionHeader(type={}, length={})".format(self.type, self.length)
+
 
 class HopByHopOption(ConvertibleToBytes):
 
@@ -724,6 +728,9 @@ class HopByHopOption(ConvertibleToBytes):
     def __len__(self):
         return len(self.header) + len(self.value)
 
+    def __repr__(self):
+        return "HopByHopOption(header={}, value={})".format(self.header, self.value)
+
 
 class MPLOption(ConvertibleToBytes):
 
@@ -766,6 +773,9 @@ class MPLOption(ConvertibleToBytes):
     def __len__(self):
         return self._header_length + self._seed_id_length[self.S]
 
+    def __repr__(self):
+        return "MPLOption(S={}, M={}, V={}, sequence={}, seed_id={})".format(self.S, self.M, self.V, self.sequence, hexlify(self.seed_id))
+
 
 class IPv6PacketFactory(PacketFactory):
 

tests/scripts/thread-cert/test_ipv6.py

@@ -259,7 +259,13 @@ def any_mpl_option():
 
 
 def any_hop_by_hop_bytes_option_header(length=4):
-    return HopByHopOptionHeader(any_type(), length)
+    _type = any_type()
+
+    # 0 or 1 means padding, so type have to be higher than 1
+    while _type <= 1:
+        _type = any_type()
+
+    return HopByHopOptionHeader(_type, length)
 
 
 def any_hop_by_hop_bytes_value(length=2):
@@ -925,7 +931,7 @@ class TestHopByHopFactory(unittest.TestCase):
                 return bytearray([0x00])
             elif padding_length > 1:
                 padding_length -= 2
-                return bytearray([0x01, padding_length]) + bytes([0x00 for _ in range(padding_length)])
+                return bytearray([0x01, padding_length]) + bytearray([0x00 for _ in range(padding_length)])
 
         return bytearray()