A transition specifies a change in a Signal at a particular point in time. (There are other ways to describe how Signals change over time. See Signal Generators - In some cases Signal Generators may provide a more compressed and accurate way of storing a Signal pattern, however at some stage during the execution of a test, the pattern will be converted to a sequence of transitions).
Transitions are used for all types of Signals (Numeric, Message, and Event). The meaning for Numeric Signals is slightly different to that for Message and Event Signals, as follows:
•Numeric - If a numeric Signal is described in terms of transitions, the Signal is assumed to remain unchanged between transitions. To get a higher resolution on the value of a Signal, reduce the time between transitions.
•Message and Event - These Signals have a value only at the instant that they occur. In this case, the transition defines the value, and the instant in time that the Message or Event occurs. (In some cases messages and events may have a NULL value. In these cases, only the time is important.)
Given the above, a transition has three main properties:
•Signal - A reference to the Signal that changes
•Time - The time at which the Signal changes
•Value - The value of the Signal at that time
A transition can also have a comment or description associated with it. If Transition Comments exist, they are displayed in a pop-up window as you mouse-over the transition in a TestCase. They are also displayed in the Transition List and in reports. You can use comments to describe the significance or cause of the transition.
In most cases, if a transition on a numeric Signal has a value identical to the previous transition, the transition is considered redundant and MxVDev discards it. However, some transitions are marked as Persistent Transitions and retained. The marking occurs in the Transform that generates the transition.
Message and Event transitions are never redundant.