Software Testing in Safety Critical Systems

Topics: Software testing, Safety, Software engineering Pages: 19 (3367 words) Published: June 2, 2014
Abstract

Today, many safety-critical applications are controlled by computer software. Therefore effective testing tools are required to provide a high degree of safety and to reduce severe failures to a minimum.

The paper examines existing regulating standards in safety-critical systems. By comparing different software testing methods the requirements and challenges in safety-critical software testing are being evaluated.

The IEC61508 standard serves as the main regulatory framework for all safetyrelated systems and provides the basis for the creation of application- and industryspecific standards. Moreover it defines certain safety integrity levels depending on the field of application and recommends testing methods according to these levels. In model-based safety testing a usage model with restricted space state domain is used to generate representative test cases. Statistical testing is a mathematical approach that uses a high number of test cases to reach a significant result. The main challenge of all safety-related testing methods is to reduce testing time and complexity without distorting the significance of the test. State domain restriction as well as importance sampling-based techniques can be used to overcome this problem.

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Table of Contents
1 Introduction.................................................................................................................5 2 Definitions...................................................................................................................6 2.1 Reliability and Safety ....................................................................................................6 2.2 Safety-Critical System States........................................................................................6 2.3 Markov Chain Usage Model .........................................................................................7

3 Standards...................................................................................................................8 4 Testing Methods.......................................................................................................11 4.1 Model-based Safety Testing........................................................................................11 4.2 Statistical Testing .......................................................................................................14 4.3 Method Comparison....................................................................................................17

5 Conclusion................................................................................................................17 Bibliography................................................................................................................19 List of Figures.............................................................................................................21 List of Acronyms.........................................................................................................22

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Introduction

1 Introduction
Today an increasing number of safety-critical systems are controlled by computers. These can for example be transportation systems, power plants, and medical applications. As people's lives depend on the correct function of such control systems and their software, thorough testing is required before they can be admitted to operation.

There are many different software testing methods. Most of them only analyze the probability of a failure but do not value its severity. However, in safety-critical systems a failure that has severe consequences, even if it is extremely rare, can not be accepted. Therefore testing in this field has to be adopted accordingly. The purpose of this paper is to find and compare the latest methods for safety-critical software testing and to identify the most common industry standard in this field. Moreover the requirements and challenges in safety-critical...

Bibliography: https://noppa.oulu.fi/noppa/kurssi/811601s/luennot/811601S_lecture_11__vuori
.pdf [accessed on 28.12.2013]
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List of Figures
List of Figures
Figure 1: Three-state Markov Model for Safety-Critical Systems(Source: [2]).............7
Figure 2: IEC 61508-3 Verification and Validation Process(Source: [6])....................10
Figure 3: Model-based Safety Testing according Gang Yu et al. (Source: [2])..........12
Figure 4: Test Case Generation Framework according Gang Yu et al. (Source: [2]).14
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