To achieve decision coverage, each branch of the decision structure in the code must be executed at least once.
The code snippet has three branches:
* withdrawal-amount <= amount-on-deposit
* withdrawal-amount <= $100 AND preferred-customer = true
* Default case where the transaction is not authorized
* Data set #1 triggers the second branch because the withdrawal amount is not less than the amount on deposit, but it is less than $100, and the user is a preferred customer.
* Data set #2 triggers the first branch where the withdrawal amount is equal to the amount on deposit.
* Data set #3 tests the condition where the withdrawal amount is less than the deposit amount, but the user is not a preferred customer, triggering the default case.
All decision branches are covered by these test cases, achieving 100% decision coverage.