2 Why We Need Model-Based Testing

52 Why We Need Model-Based Analysis
This FSM expresses all possible behaviors of the controller, so the analysis here
is complete and conclusive. This is possible because our control program has only
a few variables, each with just a few values, so it can be explored exhaustively
(completely). Our techniques can also be applied to systems that cannot be explored
exhaustively. We can configure exploration to achieve a degree of coverage that,
although incomplete, is still capable of revealing many defects (Chapter 11).
3.8 Exercises
1. Write down another run that could be executed by the controller code, which
violates the safety requirement given at the beginning of Section 3.1. Your run
must be different from both the run OutOfRangeMessageWhenIdle in Section 3.4
and the shortest path run found by the tool in Section 3.7. Confirm your run by
writing a unit test or by executing it in the simulator.
2. Write down a run that causes the controller to crash (throw an unhandled exception).
Confirm your run by writing a unit test or by executing it in the simulator.
Hint: see CheckMessage.
3. Show how to revise Controller.cs so the controller satisfies the safety and
liveness requirements given at the end of Section 3.1. Show each difference
(the contents and location of each statement that must be added, removed, or
changed). Hint: use the design rules given in Section 3.6.
Keep your revised program to use with exercises in chapters to come.
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