tests: fix mpls table check in isis_sr_flex_algo_topo1

Some test steps result in removing some entries in the MPLS forwarding
table. However, these steps pass before the entries are actually
removed.

Use the exact JSON comparison so that the removal of the entries is
checked.

Fixes: 1a61ef95b2 ("tests: add isis_sr_flex_algo_topo1 for flex-algo")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

tests/topotests/isis_sr_flex_algo_topo1/test_isis_sr_flex_algo_topo1.py

@@ -38,6 +38,7 @@ import sys
 import pytest
 import json
 import tempfile
+from copy import deepcopy
 from functools import partial
 
 # Save the Current Working Directory to find configuration files.
@@ -130,6 +131,30 @@ def setup_testcase(msg):
     return tgen
 
 
+def router_json_cmp_exact_filter(router, cmd, expected):
+    output = router.vtysh_cmd(cmd)
+    logger.info("{}: {}\n{}".format(router.name, cmd, output))
+
+    json_output = json.loads(output)
+    router_output = deepcopy(json_output)
+
+    # filter out dynamic data from "show mpls table"
+    for label, data in json_output.items():
+        if "1500" in label:
+            # filter out SR local labels
+            router_output.pop(label)
+            continue
+        nexthops = data.get("nexthops", [])
+        for i in range(len(nexthops)):
+            if "fe80::" in nexthops[i].get("nexthop"):
+                router_output.get(label).get("nexthops")[i].pop("nexthop")
+            elif "." in nexthops[i].get("nexthop"):
+                # IPv4, just checking the nexthop
+                router_output.get(label).get("nexthops")[i].pop("interface")
+
+    return topotest.json_cmp(router_output, expected, exact=True)
+
+
 def router_compare_json_output(rname, command, reference):
     "Compare router JSON output"
 
@@ -139,7 +164,9 @@ def router_compare_json_output(rname, command, reference):
     expected = json.loads(reference)
 
     # Run test function until we get an result. Wait at most 60 seconds.
-    test_func = partial(topotest.router_json_cmp, tgen.gears[rname], command, expected)
+    test_func = partial(
+        router_json_cmp_exact_filter, tgen.gears[rname], command, expected
+    )
     _, diff = topotest.run_and_expect(test_func, None, count=120, wait=0.5)
     assertmsg = '"{}" JSON output mismatches the expected result'.format(rname)
     assert diff is None, assertmsg