7CCSMASE Advanced Software Engineering

Tutorial 4

MSc Computing and Security

Design Example: A vending machine

  • Release item after receiving 15 cents
    • Single coin slot for dimes (10 ¢) and nickels (5 ¢) - assuming sensor specifies coin type
    • Machine does not give change

Draw state diagram by considering the below input sequences:

  • 3 nickels
  • 2 nickels, dime
  • Nickel, dime
  • Dime, nickel
  • Two dimes

Inputs: N, D, reset
Output: Open

What would change if, for example, the machine had the option to dispense two types of chocolate bar? There would be two buttons to choose a bar (say, one for Mars and one for Snickers) and the machine would give change.

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  1. Suppose test suite A satisfies adequacy criterion C1. Test suite B satisfies adequacy criterion C2, and C2 subsumes C1. Can we be certain that faults revealed by A will also be revealed by B?

Yes. Subsumes is a synonym for includes and thus the tests in C2(B) include the tests in C1(A).