Game Development Reference
network. Actions do not persist over time. They can be perceived, detected, or measured
when they occur but can no longer be perceived, detected, or measured some time
Only one action can be specified on a flow, but multiple operations can be represented
by a single action. An action name can appear multiple times on a TFD when each
instance carries the exact same meaning.
States represent persistent game behavior and are re-entrant. As long as you don't exit
the state you will continue to observe the same behavior, and each time you return to
the state you should detect the exact same behavior.
A state is drawn as a “bubble�? with a unique name inside. If the same behavior applies
to more than one state on your diagram, consider whether they could be the same
state. If so, remove the duplicates and reconnect the flows accordingly. Each state must
have at least one flow entering and one flow exiting.
Events, actions, and states are also referred to as primitives .
Primitive definitions provide details of the behavior represented on the TFD without
cluttering the diagram. Primitive definitions form a “data dictionary�? for the TFD.
These definitions could be in text (for example, English), a software language (for
example, C), or an executable simulation or test language (for example, TTCN). See
the “Data Dictionary�? section later in the chapter for details and examples.
These are not machines from the future programmed for war. Terminators are special
boxes placed on the TFD that indicate where testing starts and where it ends. Exactly
two terminators should appear on each TFD. One is the IN box, which normally has
a single flow that goes to a state. The other is the OUT box, which has one or more
flows entering from one or more states.
Creating a TFD is not just a matter of mechanically typing or drawing some informa-
tion you already have in another form. It is a design activity that requires the tester to
become a designer . A sound approach to getting your TFDs off and running is to go
through three stages of activities: preparation, allocation, and construction.