Introduction

This appendix contains a worked example illustrating the testing technique of State Transition analysis described in Chapter 3, which the Test Analyst can use to select specimen data for use in testing the Application Under Test (AUT) as part of the test design process.

The Testing Problem

This example describes part of the specification for the software controlling the operation of a water pump:

1. ▲ The pump can be in one of three states: Isolated, Ready, or Running. The pump cannot start (that is, move to the Running state) if it is Isolated

2. ▲ Opening the water valve will move the pump from the Isolated into the Ready state. Closing the water valve when the pump is Ready will return it to the Isolated state

3. ▲ Pressing a Start button when the pump is in the Ready state will start the pump and move it into the Running state. Pressing a Stop button when the pump is Running will stop the pump and move it into the Ready state.

Analyzing the Testing Requirements

To support the process of analyzing the above requirement, the Test Analyst draws a State Transition diagram to show graphically the states, their transitions, and the events causing those transitions (see Figure M.1).