How to create software model for testing

The reality is that modeling does not represent a new skill. Test engineers always build models. The only question is whether or not the models are in a persistent form. The ‘model’ may only exist for a short time and live on a napkin or in the mind of the engineer.
In order to write a test script or test plan, an engineer must understand the basic steps required to use the system. Modeling at the behavioral level is very similar to flowcharting; the major transactions in the use of the product are defined in a graphical format. The sequence of actions that could occur during the use of the system are defined. The actions that “could” occur also imply that that there may be more than one possible action at a specific point in the process.

There are several approaches that can be used to develop tests from a model; most of these is the concept of a path. A path is a sequence of events or actions that traverse through the model defining an actual use scenario of the system. Each element in a path, a transition or state, can have some test primitives associated with it. The primitives will define what test actions are required to move the system from its current state to the next state, verify that the state is reached or check that the system has responded properly to previous inputs. Once a path through the model has been defined, a test script can be created for that path. When this script is applied to the actual system, the actual system will follow the same sequence (or path) as defined by the model path from which the test script was extracted. This process can then be repeated for another path, which defines another use scenario, and verifies another sequence of actions. Many methods can be used to select paths, each with its own distinct objectives and advantages.

Just for example, I have shown a sample login flow chart, here we have build model for login functionality, and we mapped the paths, both successful and un successful. Now it is same thing that testers usually have in his mind, by building model, we translated our application flow in the form of model, now considering each path, we can design our test cases.

This short description is taken from the article from Larry Apfelbaum and John Doyle and login flow chart is just for sample from downloaded from google.

looking for your feedback :)