This sample models the alternating bit protocol, a simple network protocol that retransmits lost or corrupted messages (see Wikipedia.

This model is a Finite State Machine (FSM). For this simple system, it is not necessary to write a model program. This sample shows that an FSM can be used as the model (not just as a scenario machine). Just like a model program, an FSM can generate traces, generate graphics, and be composed with test suites.

The modules are:

• ABP: FSM that models the alternating bit protocol

• Scenarios: test suite with two traces, one allowed by the protocol, another not

• test: test cases with ABP that demontrate pmt options and the built-in ActionNameCoverage strategy

• test_graphics: generates ABP.svg directly from the ABP FSM using pmg without using pma, also generates ABPFSM.svg from ABP using pma, then pmg

• test_scenarios: executes Scenarios by itself, then composed with ABP to reveal that the second trace is not allowed by the model.

• fsmpy, svg: directories of FSM.py and .svg files generated by the test scripts.

You can view the .svg files in a browser.

• ABP: graph of the FSM, generated directly from ABP.py by pmg

• ABPFSM: another graph of the FSM, generated from ABP.py by pma, then pmg

There is no stepper in this sample.

Revised Apr 2013