2 Why We Need Model-Based Testing

68 Model Programs
Parameters and local variables in the model program are not state variables (there
are none in this example).
Sometimes it is useful to exclude a field from state for debugging or other
purposes. The [ExcludeFromState] attribute can be used to annotate fields that
should not be part of state. Fields excluded from the set of state variables must have
no effect on the behavior of the model.
5.4.3 Action methods
The actions of the model program are methods annotated with the [Action] attribute.
We call these methods action methods.
Each action method must express how the action changes the state (or leaves it
unchanged). Usually, the body of an action method computes the next state from
the current state, by assigning one or more state variables. These assignments are
sometimes called updates and an action method is sometimes called an update rule.
Here is the ShowTitles action method from this example. It causes the titles only
to be displayed on Topics pages by setting the style state variable to TitlesOnly.
[Action]
static void ShowTitles()
{
style = Style.TitlesOnly;
}
In addition, an action method may consume input or produce output. It is often
useful for an action method to return a value, but this is not required. An action
method may have parameters. (In this example, none of the action methods performs
input or output, returns a value, or has parameters.)
An action method can be a static method or an instance method (Chapter 15). (In
this example, they are all static.)
Action methods cannot be overloaded; each action method must have a different
name.
The action methods must all be at top level: the model program only defines
them; it cannot call them.
A model program can also contain helper methods that do not represent actions.
Any code in the model program can call a helper method. (There are no helper
methods in this example.)
5.4.4 Enabling conditions
In addition to action methods, a model program has methods that check when
each action method is enabled (allowed to be invoked). These are called enabling
more free ebooks download links at:
http://www.ebook-x.com