Requirements and System Modelling

for Verification

Understanding the System

Introduction

Before testing a new system-under-test (SUT) it is critical to actually

understand the system

One way to clarify that your understanding of the system is correct is

to generate a model of the system that is a partial, abstract

representation of the system’s desired behaviour

Once this model is in place the tester can use this to generate different

kinds of test cases

This work process can facilitate scope setting, and reduce gaps in the

test scope due to a clearer understanding of the system-under-test

Model Example

State A State B

State C

State Transition 1

State Transition 2 State Transition 3

State Transition 4

Model-based Testing [1]

The model-based testing approach is a more complex version of this

approach

Model

Abstract Tests

System

Executable Tests

are derived

from

are abstract

versions of

can be run

against

is a partial

description of

Simple is better

Model System

Executable Tests

are derived

from

can be run

against

is a partial

description of

From Requirements to Test Cases

External

Requirements

Manual Scripted Test

Cases

Model

generates Internal

Requirements

Technical

Information

Business Information

Informal Information

Other Information

Exploratory

Charters

API Tests

generates

Understanding the System

The main purpose of this exercise is to understand the system, and in

understanding the system, being able to test more effectively and

efficiently

The purpose is not to auto-generate test cases which some model-

based testing tools boast

This formalized way of modelling the system gives every tester a

hygiene understanding of the system

It is also much easier to show stakeholders the tester’s view of the

system, so that they can acknowledge this view or not

Facilitates communication and common understanding

Stakeholder Communication

Requirements Stakeholder

Requirements View

Model

Stakeholder

Tester

Review & Approve

Model

Generate Test Cases

Conclusion

This is a simple yet effective exercise which do not require any

investment in tools

By generating a model the tester gets a clearer understanding of the

system, leading to more effective and efficient testing

This model can be used to easily communicate with different

stakeholders

If you want to move to full fledged model-based testing, this could be a

first step to try out the system modelling concept

References

[1] Model-based Testing

http://en.wikipedia.org/wiki/Model-based_testing