080 seconds
We also code a run that the model program should not be able to execute:
ShowTitles(); SortByFirst(); SortByFirst(); ShowText();
The model program should not be able to execute this run because there are two
SortByFirst actions in succession. The second of these is not enabled (in the
implementation, this option is not available in this state). The run fails, confirming
that the model program cannot execute this run:
Included categories: ForbiddenRun
.Topics, WithText, ByMostRecent: ShowTitles
Topics, TitlesOnly, ByMostRecent: SortByFirst
F
Tests run: 1, Failures: 1, Not run: 0, Time: 0.080 seconds
Failures:
1) NewsReader.Tests.ForbiddenRun :
at NewsReader.Tests.ForbiddenRun()
This test failure does not indicate that the model program is incorrect. We are
not testing the model program here; we are executing the model program in order
to simulate the implemention. We are only using the test tool because it is more
convenient to write two tests than to write two applications. The failure here indicates
72 Model Programs
that the sequence of actions coded in this method is not allowed by the model
program. This means that the implementation is not able to execute this sequence.
Simulation is the most limited and labor-intensive model-based analysis technique
because it only considers one run at a time. To perform more thorough
analyses ??“ to detect the design errors discussed in Chapter 3, for example ??“ we need
to consider many different runs.
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