You are testing an ATM based on the following useATM start screen is showing1.

The most important information that is missing from this use case is the alternative behaviour, which describes the exceptional or error flows of events that may occur during the execution of the use case. For example, the use case should specify what happens if the user enters an invalid PIN, if the ATM runs out of cash, if the user cancels the transaction, etc. The alternative behaviour is essential to test the robustness and reliability of the system under test. Verified References: [ISTQB® Certified Tester Advanced Level Test Analyst CTAL-TA], Section 3.6.1, page 43.