selftests/tc-testing: add show class case for ingress qdisc

Test 0521: Show ingress class
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/tc-testing/tc-tests/qdiscs/ingress.json

@@ -98,5 +98,25 @@
         "teardown": [
             "$IP link del dev $DUMMY type dummy"
         ]
+    },
+    {
+        "id": "0521",
+        "name": "Show ingress class",
+        "category": [
+            "qdisc",
+            "ingress"
+        ],
+        "setup": [
+            "$IP link add dev $DUMMY type dummy || /bin/true"
+        ],
+        "cmdUnderTest": "$TC qdisc add dev $DUMMY ingress",
+        "expExitCode": "0",
+        "verifyCmd": "$TC class show dev $DUMMY",
+        "matchPattern": "class ingress",
+        "matchCount": "0",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY ingress",
+            "$IP link del dev $DUMMY type dummy"
+        ]
     }
 ]