feat: add tests for handling zero and negative balance scenarios in friends' balance summary

Author: Devasy

backend/tests/expenses/test_expense_service.py

@@ -2192,7 +2192,7 @@ async def test_get_friends_balance_summary_user_fetch_error(expense_service):
 
 @pytest.mark.asyncio
 async def test_get_friends_balance_summary_zero_balance_filtering(expense_service):
-    """Test that friends with zero balance are filtered out"""
+    """Test that friends with zero balance are filtered out - covers line 1061"""
     user_id_str = str(ObjectId())
 
     with patch("app.expenses.service.mongodb") as mock_mongodb:
@@ -2226,5 +2226,54 @@ async def test_get_friends_balance_summary_zero_balance_filtering(expense_servic
         assert result["summary"]["activeGroups"] == 1
 
 
+@pytest.mark.asyncio
+async def test_get_friends_balance_summary_negative_balance(expense_service):
+    """Test friends balance with negative balance (user owes) - covers line 1141"""
+    user_id_str = str(ObjectId())
+    friend_id_str = str(ObjectId())
+    group_id = str(ObjectId())
+
+    with patch("app.expenses.service.mongodb") as mock_mongodb:
+        mock_db = MagicMock()
+        mock_mongodb.database = mock_db
+
+        # Mock groups
+        mock_groups = [
+            {
+                "_id": ObjectId(group_id),
+                "name": "Test Group",
+                "members": [{"userId": user_id_str}, {"userId": friend_id_str}],
+            }
+        ]
+        mock_groups_cursor = AsyncMock()
+        mock_groups_cursor.to_list.return_value = mock_groups
+        mock_db.groups.find.return_value = mock_groups_cursor
+
+        # Mock aggregation with NEGATIVE balance (user owes friend)
+        mock_agg_cursor = AsyncMock()
+        mock_agg_cursor.to_list.return_value = [
+            {
+                "_id": friend_id_str,
+                "totalBalance": -100.0,  # Negative = user owes friend
+                "groups": [{"groupId": group_id, "balance": -100.0}],
+            }
+        ]
+        mock_db.settlements.aggregate.return_value = mock_agg_cursor
+
+        # Mock user fetch
+        mock_users_cursor = AsyncMock()
+        mock_users_cursor.to_list.return_value = [
+            {"_id": ObjectId(friend_id_str), "name": "Friend", "imageUrl": None}
+        ]
+        mock_db.users.find.return_value = mock_users_cursor
+
+        result = await expense_service.get_friends_balance_summary(user_id_str)
+
+        # Should have totalYouOwe = 100 (covers line 1141 - else branch)
+        assert result["summary"]["totalOwedToYou"] == 0
+        assert result["summary"]["totalYouOwe"] == 100.0
+        assert result["summary"]["netBalance"] == -100.0
+
+
 if __name__ == "__main__":
     pytest.main([__file__])

backend/tests/groups/test_enrich_members.py

@@ -71,7 +71,7 @@ async def test_enrich_members_with_user_details_success(self):
 
     @pytest.mark.asyncio
     async def test_enrich_members_empty_list(self):
-        """Test enrichment with empty members list"""
+        """Test enrichment with empty members list - covers line 35"""
         mock_db = MagicMock()
 
         with patch.object(self.service, "get_db", return_value=mock_db):
@@ -81,6 +81,55 @@ async def test_enrich_members_empty_list(self):
         # Verify no database call was made
         mock_db.users.find.assert_not_called()
 
+    @pytest.mark.asyncio
+    async def test_enrich_members_invalid_object_ids(self):
+        """Test enrichment with invalid ObjectIds - covers lines 46-47"""
+        members = [
+            {"userId": "invalid_id_123", "role": "admin", "joinedAt": "2023-01-01"},
+            {"userId": "also_invalid", "role": "member", "joinedAt": "2023-01-02"},
+        ]
+
+        mock_db = MagicMock()
+
+        with patch.object(self.service, "get_db", return_value=mock_db):
+            enriched = await self.service._enrich_members_with_user_details(members)
+
+        # Should return fallback members since no valid ObjectIds - covers line 52
+        assert len(enriched) == 2
+        assert "User" in enriched[0]["user"]["name"]
+        assert enriched[0]["role"] == "admin"
+
+    @pytest.mark.asyncio
+    async def test_enrich_members_member_without_userId(self):
+        """Test enrichment when member has no userId - covers line 99"""
+        user_id_1 = str(ObjectId())
+
+        members = [
+            {"userId": user_id_1, "role": "admin", "joinedAt": "2023-01-01"},
+            {"role": "member", "joinedAt": "2023-01-02"},  # No userId
+        ]
+
+        mock_users = [
+            {"_id": ObjectId(user_id_1), "name": "Admin User", "imageUrl": "admin.jpg"},
+        ]
+
+        mock_db = MagicMock()
+        mock_users_collection = MagicMock()
+        mock_db.users = mock_users_collection
+
+        mock_cursor = AsyncMock()
+        mock_cursor.to_list.return_value = mock_users
+        mock_users_collection.find.return_value = mock_cursor
+
+        with patch.object(self.service, "get_db", return_value=mock_db):
+            enriched = await self.service._enrich_members_with_user_details(members)
+
+        assert len(enriched) == 2
+        assert enriched[0]["user"]["name"] == "Admin User"
+        # Second member should be returned as-is since no userId
+        assert enriched[1]["role"] == "member"
+        assert "user" not in enriched[1] or enriched[1] == members[1]
+
     @pytest.mark.asyncio
     async def test_enrich_members_missing_user_data(self):
         """Test enrichment when some users are not found in database"""