fix: #696 test coverage back to 100%

[robbrad]

Closes #696

• GitHub Actions Workflow (behave.yml):

  • Added an environment configuration for running integration tests with a HEADLESS environment variable set to True.

• Documentation Update (CONTRIBUTING.md):

  • Added documentation to describe that Selenium-based council tests can now run in headless mode if the HEADLESS=True environment variable is set, with a link to the corresponding GitHub Actions runner setup.

• Makefile:

  • Modified unit-tests target to first erase any existing coverage data before running tests, then to append coverage results instead of overwriting.

• pytest Configuration (conftest.py):

  • Added a function to set the HEADLESS environment variable to "False" if it is not already set.

• File Handling (file_handler.py in tests/step_defs/step_helpers):

  • Updated load_json_file to handle file encoding during JSON file loading and improved error handling with more detailed logging for file loading issues.

• Integration Test Code (test_validate_council.py in tests/step_defs):

  • Added handle_test_errors as a decorator to the context fixture.
  • Revised environment variable checks and added fixtures to modularize Selenium mode setup in integration tests.

• Logging and Error Handling Enhancements (test_collect_data.py and test_common_functions.py in tests):

  • Added new unit tests for various functionalities, including valid logging setup, holiday checks using mock data, and handling input and output operations with JSON files.
  • Improved error handling and introduced mocking in tests for file operations and date checking functionalities.

• Miscellaneous Code Updates:

  • Various changes to enhance robustness, error handling, and testability of the codebase, especially focusing on JSON data management and Selenium WebDriver setup.

[robbrad]

@dp247 if you would be so kind sir :)

[dp247]

Yooo, that's a lot of changes! It'll take me a little bit just to make sure I'm reviewing carefully, but looks good so far!