Status: IN
Some solution files (e.g., `largest-number-after-digit-swaps-by-parity`, `largest-odd-number-in-string`) contain both the `Solution` class and a `unittest.TestCase` class in the same module, while others keep tests in a separate `test_solution.py`
Source: entries/2026/06/06/largest-number-after-digit-swaps-by-parity-solution.md