Add comprehensive tests for Groups API (24 tests)

Tests include:
- Group model validation (8 tests)
  - Group, GroupCreate, GroupUpdate models
  - Field validation, name validation
  - Minimal and full field tests

- Sync GroupsEndpoint (8 tests)
  - List, get, create, update, delete operations
  - User assignment/unassignment operations
  - Validation error handling

- Async AsyncGroupsEndpoint (8 tests)
  - Complete async coverage matching sync API
  - All CRUD operations tested
  - User management operations

All 24 tests passing. Achieves comprehensive coverage for Groups API.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/models/test_group.py

@@ -0,0 +1,109 @@
+"""Tests for Group data models."""
+
+import pytest
+from pydantic import ValidationError
+
+from wikijs.models import Group, GroupCreate, GroupUpdate
+
+
+class TestGroup:
+    """Test Group model."""
+
+    def test_group_creation_minimal(self):
+        """Test creating a group with minimal fields."""
+        group = Group(
+            id=1,
+            name="Administrators",
+            created_at="2024-01-01T00:00:00Z",
+            updated_at="2024-01-01T00:00:00Z",
+        )
+        assert group.id == 1
+        assert group.name == "Administrators"
+        assert group.is_system is False
+        assert group.permissions == []
+        assert group.page_rules == []
+        assert group.users == []
+
+    def test_group_creation_full(self):
+        """Test creating a group with all fields."""
+        group = Group(
+            id=1,
+            name="Editors",
+            is_system=False,
+            redirect_on_login="/dashboard",
+            permissions=["read:pages", "write:pages"],
+            page_rules=[
+                {"id": "1", "path": "/docs/*", "roles": ["write"], "match": "START"}
+            ],
+            users=[{"id": 1, "name": "John Doe", "email": "john@example.com"}],
+            created_at="2024-01-01T00:00:00Z",
+            updated_at="2024-01-01T00:00:00Z",
+        )
+        assert group.name == "Editors"
+        assert group.redirect_on_login == "/dashboard"
+        assert len(group.permissions) == 2
+        assert len(group.page_rules) == 1
+        assert len(group.users) == 1
+
+    def test_group_name_validation(self):
+        """Test name validation."""
+        # Too short
+        with pytest.raises(ValidationError):
+            Group(
+                id=1,
+                name="",
+                created_at="2024-01-01T00:00:00Z",
+                updated_at="2024-01-01T00:00:00Z",
+            )
+
+        # Too long
+        with pytest.raises(ValidationError):
+            Group(
+                id=1,
+                name="x" * 256,
+                created_at="2024-01-01T00:00:00Z",
+                updated_at="2024-01-01T00:00:00Z",
+            )
+
+
+class TestGroupCreate:
+    """Test GroupCreate model."""
+
+    def test_group_create_minimal(self):
+        """Test creating group with minimal fields."""
+        group_data = GroupCreate(name="Test Group")
+        assert group_data.name == "Test Group"
+        assert group_data.permissions == []
+        assert group_data.page_rules == []
+
+    def test_group_create_full(self):
+        """Test creating group with all fields."""
+        group_data = GroupCreate(
+            name="Test Group",
+            redirect_on_login="/home",
+            permissions=["read:pages"],
+            page_rules=[{"path": "/*", "roles": ["read"]}],
+        )
+        assert group_data.redirect_on_login == "/home"
+        assert len(group_data.permissions) == 1
+
+    def test_group_create_name_validation(self):
+        """Test name validation."""
+        with pytest.raises(ValidationError):
+            GroupCreate(name="")
+
+
+class TestGroupUpdate:
+    """Test GroupUpdate model."""
+
+    def test_group_update_empty(self):
+        """Test empty update."""
+        update_data = GroupUpdate()
+        assert update_data.name is None
+        assert update_data.permissions is None
+
+    def test_group_update_partial(self):
+        """Test partial update."""
+        update_data = GroupUpdate(name="Updated Name")
+        assert update_data.name == "Updated Name"
+        assert update_data.permissions is None