# T05: Add JSON Output

Add the exact option `--format json` to `python3 -m ledger summary`. Default output without the option must keep baseline behavior. The JSON must be readable by a standard JSON parser and contain the fields `count`, `total_cents`, and `by_category`; amounts are integer cents, `by_category` keys are the original category text and values are that category's total in integer cents, with keys ordered by ascending Unicode code point. Identical input must produce stable output; stdout must contain only JSON — no logs or explanatory text mixed in.

Add tests and a short usage note for the new option; do not delete or modify existing tests or add runtime dependencies. Run `python3 -m unittest discover -s tests -v` and report the actual result.