![What is the cost of defects?
As well as considering the impact of failures arising from defects we
have not found, we need to consider the impact of when we find those
defects. The cost of finding and fixing defects rises considerably across the
life cycle
If we relate the scenarios mentioned previously to Figure 1.2, we see
that, if an error is made and the consequent defect is detected in the
requirements at the specification stage, then it is relatively cheap to find
and fix. The observation of increasing defect-removal costs in software
traces back to [Boehm]. You'll find evidence for the economics of testing
and other quality assurance activities in [Gilb], [Black 2001] or [Black
2004].](https://image.slidesharecdn.com/fundamentalsoftesting-andikadwiarycandra-171211072332/85/Fundamentals-of-Testing-Andika-Dwi-Ary-Candra-7-320.jpg)
![We may also be required to carry out software testing to meet
contractual or legal requirements, or industry-specific
standards. The avionics, motor, medical and pharmaceutical
industries all have standards covering the testing of software.
For example, the US Federal Aviation Administration's DO-178B
standard [RTCA/DO-178B] has requirements for test coverage](https://image.slidesharecdn.com/fundamentalsoftesting-andikadwiarycandra-171211072332/85/Fundamentals-of-Testing-Andika-Dwi-Ary-Candra-11-320.jpg)
Fundamentals of Testing - Andika Dwi Ary Candra
- 1. FUNDAMENTALS OF TESTING Andika Dwi Ary Candra Information System Sains and Technology UIN SUSKA RIAU
- 2. Introduce We'll describe and illustrate how software defects or bugs cause problems for people, the environment or a company. We'll important distinctions between defects, their root causes and effects. We'll explain why testing is necessary to find these how testing promotes quality, and how testing fits into quality assurance. In this section, we will also introduce some principles of testing. As we go through this section, watch for the Syllabus terms defect, error, failure, fault, mistake, quality, risk, software, testing and exhaustive testing. You'll find these terms defined in the glossary.
- 3. Software systems context Testing Principle - Testing is context dependent Testing is done differently in different contexts. For example, safety-critical software is tested differently from an e- site. These days, almost everyone is aware of software We encounter them in our homes, at work, while shopping, because of mass communication systems. More and more, are part of our lives. . Not all software systems carry the same level of risk and not all problems have the same impact when occur. A risk is something that has not happened yet and it never happen; it is a potential problem.
- 4. Causes of software defects Why is it that software systems sometimes don't work We know that people make mistakes - we are fallible. If someone makes an error or mistake in using the software, may lead directly to a problem - the software is used incorrectly so does not behave as we expected. However, people also build the software and they can make mistakes during the build. These mistakes mean that there are flaws in the software These are called defects or sometimes bugs or faults. software is not just the code; check the definition of soft- ware to remind yourself.
- 5. When we think about what might go wrong we have to consider defects and failures arising from: 1. errors in the specification, design and implementation of the software and system; 2. errors in use of the system; 3. environmental conditions; 4. intentional damage; 5. potential consequences of earlier errors, 6. intentional damage, defects and failures.
- 6. When do defects arise? In Figure 1.1 we can see how defects may arise in four requirements for a product.
- 7. What is the cost of defects? As well as considering the impact of failures arising from defects we have not found, we need to consider the impact of when we find those defects. The cost of finding and fixing defects rises considerably across the life cycle If we relate the scenarios mentioned previously to Figure 1.2, we see that, if an error is made and the consequent defect is detected in the requirements at the specification stage, then it is relatively cheap to find and fix. The observation of increasing defect-removal costs in software traces back to [Boehm]. You'll find evidence for the economics of testing and other quality assurance activities in [Gilb], [Black 2001] or [Black 2004].
- 8. The specification can be corrected and re-issued. Similarly if an error is made and the consequent defect detected in the design at the design stage then the design can be corrected and re-issued with relatively little expense. The same applies for construction. If however a defect is introduced in the requirement specification and it is not detected until acceptance testing or even once the system has been implemented then it will be much more expensive to fix. This is because rework will be needed in the specification and design before changes can be made in con- struction; because one defect in the requirements may well propagate into several places in the design and code; and because all the testing work done-to that point will need to be repeated in order to reach the confidence level in the software that we require
- 9. It is quite often the case that defects detected at a very late stage, depending on how serious they are, are not corrected because the cost of doing so is too expensive. Also, if the software is delivered and meets an agreed specification, it sometimes still won't be accepted if the specification was wrong. The project team may have delivered exactly what they were asked to deliver, but it is not what the users wanted. This can lead to users being unhappy with the system that is finally delivered. In some cases, where the defect is too serious, the system may have to be de-installed completely.
- 10. Role of testing in software development, maintenance and operations Rigorous testing is necessary during development and maintenance identify defects, in order to reduce failures in the operational and increase the quality of the operational system. This includes looking for places in the user interface where a user make a mistake in input of data or in the interpretation of the output, looking for potential weak points for intentional and malicious attack. Executing tests helps us move towards improved quality of product and service, but that is just one of the verification and validation methods to products. Processes are also checked, for example by audit. A variety methods may be used to check work, some of which are done by the the work and some by others to get an independent view.
- 11. We may also be required to carry out software testing to meet contractual or legal requirements, or industry-specific standards. The avionics, motor, medical and pharmaceutical industries all have standards covering the testing of software. For example, the US Federal Aviation Administration's DO-178B standard [RTCA/DO-178B] has requirements for test coverage
- 12. Testing and quality Testing helps us to measure the quality of software in terms of the number of defects found, the tests run, and the system covered by the can do this for both the functional attributes of the software (for example, printing a report correctly) and for the non-functional software and characteristics (for example, printing a report quickly enough What is quality? Projects aim to deliver software to specification. For the project to the customer needs requires a correct specification. Additionally, the system must meet the specification. This is known as validation ('is this right specification?') and verification ('is the system correct to
- 13. BIBLIOGRAPHY Graham et.al.(2011). ISTBQ-Fondation Of Software Testing London : Cengage Learning EMEA.
- 15. THANK YOU