FIN-12 · Ledger audit failed
Auditors found three problems in bank/ledger.py:
- Opening a new account shows other customers' transactions in its history (and tags).
- Balances drift:
0.1 + 0.2 shows as 0.30000000000000004.
- A transfer to an unknown account debited the sender anyway, and someone withdrew a negative amount to mint money.
Make tests/test_ledger.py pass. This is plain Python (unittest).