UC 18: Customer Checkout [adapted from Fowler p.40]

1. Customer browses through the catalog and selects items to buy and then
goes to check out.

2. System responds with shipping selection menu.

3. Customer fills in shipping information (address, next-day or 3-day).

4. System presents full pricing information, including shipping.

5. Customer fills in credit card information.

6. System prompts for final authorization (are you sure?).

7. Customer authorizes purchase and credit card charge.

8. System attempts credit card validation.

9. Authorization successful. System confirms sale to user.

10. System sends confirming email. Terminate use case.

Extensions:

2a. For regular customer, system displays current shipping information, pricing
information, and last four digits of credit card information. Customer may accept or override these defaults. Return to step 6 or customer cancel terminates use case.

3b. Customer cancels transaction. Terminate use case.

5a. Customer cancels transaction. Terminate use case.

7a. Customer cancels transaction. Terminate use case.

9a. System fails to authorize credit purchase. Allow customer to re-enter credit card information. Return to step 4.