test(notepad): expand unit tests for NotepadComponent operations

- Added comprehensive tests for adding, removing, and editing values in the NotepadComponent, covering edge cases such as out-of-range positions and invalid operations.
- Implemented tests to ensure correct behavior when handling negative positions and positions beyond the notepad length, confirming that values are appended correctly.
- Validated error handling for invalid removal operations, ensuring appropriate exceptions are raised and the notepad state remains unchanged when necessary.
- Enhanced test coverage for multiple notepad instances, verifying that each notepad maintains its own content independently.

These changes improve the reliability and robustness of the NotepadComponent by ensuring thorough testing of its functionalities.

src/backend/tests/unit/components/helpers/test_notepad_component.py

@@ -178,3 +178,117 @@ async def test_persistence_between_operations(self, component_class):
         # Step 4: Verify only "Value 2" remains
         assert len(result3) == 1
         assert result3.iloc[0]["value"] == "Value 2"
+
+    async def test_add_value_out_of_range_position(self, component_class):
+        """Test adding values with out-of-range positions.
+
+        Values should be appended at the end when position is:
+        - Negative
+        - Beyond the notepad length
+        """
+        component: NotepadComponent = component_class(input_value="First Value", operation="add")
+        self._add_mock_vertex(component)
+        await component.process_and_get_notepad()
+
+        # Test negative position
+        component = component.set(input_value="Second Value", operation="add", position=-1)
+        result = await component.process_and_get_notepad()
+        assert len(result) == 2
+        assert result.iloc[-1]["value"] == "Second Value"
+
+        # Test position beyond length
+        component = component.set(input_value="Third Value", operation="add", position=10)
+        result = await component.process_and_get_notepad()
+        assert len(result) == 3
+        assert result.iloc[-1]["value"] == "Third Value"
+
+    async def test_remove_value_invalid_cases(self, component_class):
+        """Test removing values with invalid inputs.
+
+        Tests:
+        - Removing with invalid positions raises ValueError
+        - Removing non-existent values leaves notepad unchanged
+        - Removing from empty notepad leaves notepad unchanged
+        """
+        # Setup initial data
+        component: NotepadComponent = component_class(input_value="Value 1", operation="add")
+        self._add_mock_vertex(component)
+        await component.process_and_get_notepad()
+
+        # Test removing with invalid position (negative)
+        component = component.set(operation="remove", position=-1)
+        with pytest.raises(
+            ValueError, match="Error performing operation remove on notepad: Position -1 is out of bounds"
+        ):
+            await component.process_and_get_notepad()
+
+        # Test removing with position beyond length
+        component = component.set(operation="remove", position=10)
+        with pytest.raises(
+            ValueError, match="Error performing operation remove on notepad: Position 10 is out of bounds"
+        ):
+            await component.process_and_get_notepad()
+
+        # Test removing non-existent value (should leave notepad unchanged)
+        # Reset position to None for value-based removal
+        component = component.set(operation="remove", input_value="Non-existent Value", position=None)
+        result = await component.process_and_get_notepad()
+        assert len(result) == 1  # Notepad should remain unchanged
+
+        # Create empty notepad for empty notepad test
+        empty_component: NotepadComponent = component_class(operation="remove")
+        self._add_mock_vertex(empty_component)
+        result = await empty_component.process_and_get_notepad()
+        assert len(result) == 0  # Should handle empty notepad gracefully
+
+    async def test_edit_value_edge_cases(self, component_class):
+        """Test editing values with edge cases.
+
+        Tests:
+        - Editing with invalid positions
+        - Editing the last row when position is beyond length
+        """
+        # Setup initial data
+        component: NotepadComponent = component_class(input_value="Original", operation="add")
+        self._add_mock_vertex(component)
+        await component.process_and_get_notepad()
+
+        # Add second value
+        component = component.set(input_value="Second", operation="add")
+        await component.process_and_get_notepad()
+
+        # Test editing with negative position (should edit last row)
+        component = component.set(operation="edit", input_value="Modified Last", position=-1)
+        result = await component.process_and_get_notepad()
+        assert result.iloc[-1]["value"] == "Modified Last"
+
+        # Test editing with position beyond length (should edit last row)
+        component = component.set(operation="edit", input_value="Modified Beyond", position=10)
+        result = await component.process_and_get_notepad()
+        assert result.iloc[-1]["value"] == "Modified Beyond"
+
+    async def test_invalid_operation(self, component_class):
+        """Test that invalid operations raise appropriate errors."""
+        component: NotepadComponent = component_class(input_value="Test", operation="invalid_op")
+        self._add_mock_vertex(component)
+
+        with pytest.raises(ValueError, match="Invalid operation: invalid_op"):
+            await component.process_and_get_notepad()
+
+    async def test_multiple_notepad_instances(self, component_class):
+        """Test that multiple notepads can be managed using different notepad names."""
+        # Create first notepad
+        component1: NotepadComponent = component_class(input_value="Value 1", operation="add", notepad_name="notepad1")
+        self._add_mock_vertex(component1)
+        result1 = await component1.process_and_get_notepad()
+
+        # Create second notepad
+        component2: NotepadComponent = component_class(input_value="Value 2", operation="add", notepad_name="notepad2")
+        self._add_mock_vertex(component2)
+        result2 = await component2.process_and_get_notepad()
+
+        # Verify each notepad has its own content
+        assert len(result1) == 1
+        assert len(result2) == 1
+        assert result1.iloc[0]["value"] == "Value 1"
+        assert result2.iloc[0]["value"] == "Value 2"