tests: change GID of a group

This is the transformation to Python of the test located in
`tests/grouptools/groupmod/01_groupmod_change_gid/groupmod.test`, which
checks that `groupmod` is able to change the GID of a group.

Signed-off-by: Iker Pedrosa <ipedrosa@redhat.com>

tests/system/tests/test_groupmod.py

@@ -0,0 +1,32 @@
+"""
+Test groupmod
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from framework.roles.shadow import Shadow
+from framework.topology import KnownTopology
+
+
+@pytest.mark.topology(KnownTopology.Shadow)
+def test_groupmod__change_gid(shadow: Shadow):
+    """
+    :title: Change the GID of a group
+    :setup:
+        1. Create group
+        2. Change GID
+    :steps:
+        1. Group exists and GID is 1001
+    :expectedresults:
+        1. Group is found and GID matches
+    :customerscenario: False
+    """
+    shadow.groupadd("tgroup")
+    shadow.groupmod("-g 1001 tgroup")
+
+    result = shadow.tools.getent.group("tgroup")
+    assert result is not None, "Group should be found"
+    assert result.name == "tgroup", "Incorrect groupname"
+    assert result.gid == 1001, "Incorrect GID"