diff --git a/tests/system/framework/utils/tools.py b/tests/system/framework/utils/tools.py
index a2c85cba4b..03a79219af 100644
--- a/tests/system/framework/utils/tools.py
+++ b/tests/system/framework/utils/tools.py
@@ -388,8 +388,8 @@ def __init__(
         self,
         name: str | None,
         password: str | None,
-        administrators: str | None,
-        members: str | None,
+        administrators: list[str],
+        members: list[str],
     ) -> None:
         self.name: str | None = name
         """
@@ -401,18 +401,18 @@ def __init__(
         Group password.
         """
 
-        self.administrators: str | None = administrators
+        self.administrators: list[str] = administrators
         """
         Group administrators.
         """
 
-        self.members: str | None = members
+        self.members: list[str] = members
         """
         Group members.
         """
 
     def __str__(self) -> str:
-        return f"({self.name}:{self.password}:{self.administrators}:" f"{self.members})"
+        return f"({self.name}:{self.password}:" f"{self.administrators}:" f"{self.members})"
 
     def __repr__(self) -> str:
         return str(self)
@@ -422,7 +422,7 @@ def FromDict(cls, d: dict[str, Any]) -> GShadowEntry:
         return cls(
             name=d.get("group_name", None),
             password=d.get("password", None),
-            administrators=d.get("administrators", None),
+            administrators=d.get("administrators", []),
             members=d.get("members", []),
         )
 
diff --git a/tests/system/tests/test_groupmod.py b/tests/system/tests/test_groupmod.py
index 6617602f5b..40aa38484e 100644
--- a/tests/system/tests/test_groupmod.py
+++ b/tests/system/tests/test_groupmod.py
@@ -69,3 +69,63 @@ def test_groupmod__u_option_empty_string_clears_members(shadow: Shadow):
         assert gshadow_entry is not None, "Group should be found"
         assert gshadow_entry.name == "tgroup", "Incorrect groupname"
         assert not gshadow_entry.members, "Group should have no members"
+
+
+@pytest.mark.topology(KnownTopology.Shadow)
+def test_groupmod__u_option_with_user_list(shadow: Shadow):
+    """
+    :title: Test groupmod -U option with user list to set group membership
+    :setup:
+        1. Create three test users
+        2. Create test group
+    :steps:
+        1. Set group membership to all three users using groupmod -U
+        2. Verify all three users are members in group and gshadow entry
+        3. Modify group membership to only two users using groupmod -U
+        4. Verify updated membership in group and gshadow entries
+    :expectedresults:
+        1. Initial groupmod -U command sets membership correctly for all three users
+        2. group and gshadow entries show correct membership
+        3. Second groupmod -U command updates membership correctly
+        4. Updated group and gshadow entries reflect new membership
+    :customerscenario: False
+    """
+    shadow.useradd("tuser1")
+    shadow.useradd("tuser2")
+    shadow.useradd("tuser3")
+    shadow.groupadd("tgroup")
+    shadow.groupmod("-U tuser1,tuser2,tuser3 tgroup")
+
+    group_entry = shadow.tools.getent.group("tgroup")
+    assert group_entry is not None, "Group should be found"
+    assert group_entry.name == "tgroup", "Incorrect groupname"
+    assert len(group_entry.members) == 3, f"Group should have 3 members, but has {len(group_entry.members)}"
+    assert "tuser1" in group_entry.members, "tuser1 should be a member of tgroup"
+    assert "tuser2" in group_entry.members, "tuser2 should be a member of tgroup"
+    assert "tuser3" in group_entry.members, "tuser3 should be a member of tgroup"
+
+    if shadow.host.features["gshadow"]:
+        gshadow_entry = shadow.tools.getent.gshadow("tgroup")
+        assert gshadow_entry is not None, "Group should be found"
+        assert gshadow_entry.name == "tgroup", "Incorrect groupname"
+        assert len(gshadow_entry.members) == 3, f"Group should have 3 members, but has {len(gshadow_entry.members)}"
+        assert "tuser1" in gshadow_entry.members, "tuser1 should be a member of tgroup"
+        assert "tuser2" in gshadow_entry.members, "tuser2 should be a member of tgroup"
+        assert "tuser3" in gshadow_entry.members, "tuser3 should be a member of tgroup"
+
+    shadow.groupmod("-U tuser1,tuser2 tgroup")
+
+    group_entry = shadow.tools.getent.group("tgroup")
+    assert group_entry is not None, "Group should be found"
+    assert group_entry.name == "tgroup", "Incorrect groupname"
+    assert len(group_entry.members) == 2, f"Group should have 2 members, but has {len(group_entry.members)}"
+    assert "tuser1" in group_entry.members, "tuser1 should be a member of tgroup"
+    assert "tuser2" in group_entry.members, "tuser2 should be a member of tgroup"
+
+    if shadow.host.features["gshadow"]:
+        gshadow_entry = shadow.tools.getent.gshadow("tgroup")
+        assert gshadow_entry is not None, "Group should be found"
+        assert gshadow_entry.name == "tgroup", "Incorrect groupname"
+        assert len(gshadow_entry.members) == 2, f"Group should have 2 members, but has {len(gshadow_entry.members)}"
+        assert "tuser1" in gshadow_entry.members, "tuser1 should be a member of tgroup"
+        assert "tuser2" in gshadow_entry.members, "tuser2 should be a member of tgroup"