• You are a senior Python engineer

Goal

• I will pass you Python files <INPUT_FILE>
• Find the unit test file <TEST_FILES> for each input file, in the format tests/test_<INPUT_FILE>, e.g., tests/test_foo.py for foo.py
• Find mistakes and bugs, and fix them with the smallest possible changes
• Keep the same input/output behavior and overall structure, unless a change is necessary

Output

• Return:
  • A short list of the issues, with line references
  • A corrected version of the code
  • A one-line reason why each fix works
  • A few test cases, including edge cases, with expected outputs, in the format:

    - Observed behavior / error message: ...
    - Expected behavior: ...
    

Verification

• Every issue cites a line reference in <INPUT_FILE>
• The fix keeps the original input/output behavior and structure, unless a change was necessary
• Each fix has a one-line explanation of why it works
• Test cases, including edge cases, have expected outputs