Add comprehensive unit tests for core modules

[Copilot]

Added extensive unit test coverage for 5 core modules that previously lacked testing:

New Test Files Added

• test_preprocessamento.py (5 tests) - Tests for text preprocessing utilities including accent removal with various edge cases
• test_exceptions.py (6 tests) - Tests for all custom exception classes including HTTP exceptions and parser errors
• test_authentication.py (6 tests) - Tests for token verification with proper mocking of environment variables
• test_servico_llm.py (5 tests) - Tests for LLM service functions with comprehensive mocking of external API calls
• test_constants.py (12 tests) - Tests for configuration constants, ENEM themes validation, and environment variable loading

Key Features

• 34 new test cases providing comprehensive coverage for previously untested modules
• No external dependencies - All tests use proper mocking to avoid network calls
• Follows existing patterns - Uses the same unittest framework and coding style as existing tests
• Edge case coverage - Tests handle empty inputs, invalid data, and error conditions
• Environment isolation - Tests properly set up and tear down environment variables

Technical Improvements

• Modified authentication.py to read environment variables within functions for better testability
• All new tests are self-contained and don't require internet connectivity
• Used comprehensive mocking for external API dependencies
• Ensured compatibility with existing test infrastructure

Test Results

Ran 34 tests in 0.011s
OK

All new tests pass successfully and provide robust coverage for the core functionality.

Fixes #23.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• huggingface.co
  • Triggering command: python -m unittest discover tests/ -v (dns block)
  • Triggering command: python -m unittest discover tests/ -k test_preprocessamento or test_exceptions or test_authentication or test_servico_llm or test_constants -v (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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