How do you write test cases on vending machine?

To write test cases for a vending machine, first identify key functionalities such as item selection, payment processing, and item dispensing. Create test cases that cover various scenariOS, including valid and invalid inputs (e.g., selecting an item that is out of stock), testing different payment methods (cash, card), and verifying the correct change is returned. Additionally, include edge cases like handling insufficient funds or selecting multiple items. Each test case should outline the input, expected output, and the criteria for success.