This commit introduces a new test suite for the Python scripts located in the examples/travel/ directory.

Key changes:
- Created a new subdirectory examples/travel/tests/.
- Added an __init__.py file to examples/travel/tests/ to make it a Python package.
- For each script in examples/travel/ (add_hotel_ad.py, add_hotel_ad_group_bid_modifiers.py, add_hotel_listing_group_tree.py, add_performance_max_for_travel_goals_campaign.py, add_things_to_do_ad.py):
    - A corresponding test file (e.g., test_add_hotel_ad.py) was created in examples/travel/tests/.
    - Each test file includes unittest.TestCase classes with methods to test the main functionality of the script.
    - Tests utilize unittest.mock to mock the GoogleAdsClient, its services, and API responses, ensuring that no actual API calls are made.
    - Assertions are in place to verify that:
        - GoogleAdsClient is loaded with version "v19".
        - Service methods are called with the expected parameters.
        - Helper functions within the scripts behave as intended.
        - Command-line arguments are parsed correctly.
        - The script produces the expected print outputs.
- The tests are structured to be discoverable and runnable from the root directory of the repository (e.g., using `python -m unittest discover ./examples/travel/tests`).

This test suite improves the robustness and maintainability of the example scripts by providing automated checks for their core logic.

… done so far and provide feedback for Jules to continue.

This commit completes the creation and debugging of a test suite for Python scripts in the examples/travel/ directory.

Summary of steps and changes:

1.  **Initial Test Creation**:
    *   I created the `examples/travel/tests/` directory and `__init__.py`.
    *   I generated initial test files for all 5 scripts:
        *   `test_add_hotel_ad.py`
        *   `test_add_hotel_ad_group_bid_modifiers.py`
        *   `test_add_hotel_listing_group_tree.py`
        *   `test_add_performance_max_for_travel_goals_campaign.py`
        *   `test_add_things_to_do_ad.py`

2.  **Debugging and Refinement**:
    *   **Common Test Structure**: I refactored the tests to remove `test_script_runner` methods, which unreliably tested `if __name__ == "__main__":` blocks. Instead, I focused `test_main` methods on the core script logic, directly passing a mocked `GoogleAdsClient` instance.
    *   **Script Correction**: I identified and fixed f-string errors in print statements within `examples/travel/add_hotel_ad.py`.
    *   **Enum Mocking**: I resolved an `AttributeError` in `test_add_performance_max_for_travel_goals_campaign.py` by ensuring mocked enum objects correctly provided a `.name` string attribute.
    *   **Mocking Complexities (`test_add_hotel_listing_group_tree.py`)**:
        *   I encountered significant difficulties mocking protobuf `Message.CopyFrom()` calls and reliably asserting direct attribute assignments on nested `MagicMock` objects.
        *   **Resolution**: I simplified assertions for this test to focus on reliably verifiable aspects: service call invocation, correct `customer_id`, expected number of operations, calls to `client.get_type` for key messages, calls to `client.copy_from` (the client utility, not the protobuf method), and print statements. This acknowledges the mocking limitations while still providing value.
    *   **Dynamic Type Mocking**: For `test_add_things_to_do_ad.py` and `test_add_performance_max_for_travel_goals_campaign.py`, I implemented a dynamic side effect for `client.get_type` to ensure that mocked types had necessary child attributes (as `MagicMock` instances) pre-configured. This prevented `AttributeError`s when the script accessed nested attributes on these mocked types.

3.  **Final Verification**:
    *   I confirmed that all individual test files passed.
    *   I ran `python -m unittest discover ./examples/travel/tests`, and all 5 tests passed successfully.

All planned work for this issue is now complete and included in this commit.