Task:
  Design a test plan for an e-commerce checkout system.


Success Criteria:
  - List at least 10 functional requirements for the checkout system.
  - Provide measurable success criteria for each requirement.


Examples:
  - Normal case: Functional requirement could be 'User can add items to the cart.'
  - Edge case: Functional requirement could be 'System handles out-of-stock items gracefully.'
