2 Why We Need Model-Based Testing

102 Exploring and Analyzing Finite Model Programs
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0
SelectMessages()
ShowTitles()
Figure 6.5. Simulation by interactive exploration (1).
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2
SelectMessages() ShowTitles() ShowText()
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2
SelectMessages()
Figure 6.6. Simulation by interactive exploration (2).
SortByFirst()
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and select SortByFirst by selecting its next state (Figure 6.5). Proceeding in this
way, we can simulate the entire run. 3
Interactive exploration can also show that a run is not allowed. If we attempt
to explore the second run that we tested in Chapter 5, we find that after the first
SortByFirst transition, the second SortByFirst transition is not enabled, so it is not
possible to execute that run.
It is not always obvious whether or not a particular run (that you might write down)
is allowed by a model program. As we have shown here, interactive exploration is one
way to determine this. But, like any interactive procedure, it is not fully automated
so it can be time-consuming and difficult to repeat. In Chapter 7 we describe another,
3 In mpv, select the initial node with the mouse, press the Delete key to hide all the other states
and transitions, press Enter to display the enabled transitions, press n (next) and p (previous) to
select another node, and so on.
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