Is your feature request related to a problem? Please describe.
There are currently no automated tests for article.py, making it difficult to ensure that the Article class and its methods work as intended and to catch regressions during development.

Describe 1~3 use cases of the purposed feature

• Verify that the Article class can be instantiated and its properties (such as key, bytes, words, etc.) return expected values.
• Ensure that methods like add_revision, link, and equality/hash operations behave correctly.
• Confirm that edge cases (e.g., articles with no revisions, or with only redirects) are handled gracefully.

Describe alternatives you've considered

• Relying on manual testing or indirect coverage through higher-level tests, but this does not guarantee that all code paths in article.py are exercised.
• Adding only integration tests, which may not catch issues specific to the Article class.

Additional context
Unit tests for article.py will help maintain code quality and reliability. Tests could be implemented using pytest or unittest, and should cover both typical and edge-case usage of the Article class.