Add a testcase for GNOI OS.Verify. (sonic-net#16770)

Description of PR
Summary:
Add a testcase for GNOI OS.Verify.

Approach
What is the motivation for this PR?
Add a testcase for GNOI OS.Verify.

How did you do it?
Add a testcase for GNOI OS.Verify.

How did you verify/test it?
On physical switch:
with an up to date image

Author: hdwhdw

tests/gnmi/helper.py

@@ -1,6 +1,7 @@
 import time
 import logging
 import pytest
+import json
 from tests.common.utilities import wait_until
 from tests.common.helpers.gnmi_utils import GNMIEnvironment
 
@@ -452,3 +453,25 @@ def gnoi_request(duthost, localhost, module, rpc, request_json_data):
         return -1, output['stderr']
     else:
         return 0, output['stdout']
+
+
+def extract_gnoi_response(output):
+    """
+    Extract the JSON response from the gNOI client output
+
+    Args:
+        output: gNOI client output, the output is in the form of
+                "Module RPC: <JSON response>", e.g. "System Time\n {"time":1735921221909617549}"
+
+    Returns:
+        json response: JSON response extracted from the output
+    """
+    try:
+        if '\n' not in output:
+            logging.error("Invalid output format: {}, expecting 'Module RPC: <JSON response>'.".format(output))
+            return None
+        response_line = output.split('\n')[1]
+        return json.loads(response_line)
+    except json.JSONDecodeError:
+        logging.error("Failed to parse JSON: {}".format(response_line))
+        return None

tests/gnmi/test_gnoi_os.py

@@ -0,0 +1,36 @@
+import pytest
+import logging
+
+from .helper import gnoi_request, extract_gnoi_response
+from tests.common.helpers.assertions import pytest_assert
+
+pytestmark = [
+    pytest.mark.topology('any')
+]
+
+"""
+This module contains tests for the gNOI OS API.
+"""
+
+
+@pytest.mark.disable_loganalyzer
+def test_gnoi_os_verify(duthosts, rand_one_dut_hostname, localhost):
+    """
+    Verify the gNOI OS Verify API returns the current OS version.
+    """
+    duthost = duthosts[rand_one_dut_hostname]
+
+    # Get current OS version
+    ret, msg = gnoi_request(duthost, localhost, "OS", "Verify", "")
+    pytest_assert(ret == 0, "OS.Verify API reported failure (rc = {}) with message: {}".format(ret, msg))
+    logging.info("OS.Verify API returned msg: {}".format(msg))
+    # Message should contain a json substring like this {"version":"SONiC-OS-20240510.24"}
+    # Extract JSON part from the message
+    msg_json = extract_gnoi_response(msg)
+    if not msg_json:
+        pytest.fail("Failed to extract JSON from OS.Verify API response")
+    logging.info("Extracted JSON: {}".format(msg_json))
+    pytest_assert("version" in msg_json, "OS.Verify API did not return os_version")
+
+    os_version_ansible = duthost.image_facts()["ansible_facts"]["ansible_image_facts"]["current"]
+    pytest_assert(msg_json["version"] == os_version_ansible, "OS.Verify API returned incorrect OS version")