Fundamentals of testing
- 2. In this chapter,we will introduce you to the fundamentals of testing:why testing is needed; its limitations,objective sand purpose;the principles behind testing; the process that testers follow; and some of the psychological factors that testers must consider in their work. By reading this chapter you'll gain an understanding of the fundamentals of testing and be able to describe those fundamentals.
- 3. In this section, we're going to kick off the book with a discussion on why testing matters. We'll describe and illustrate how software defects or bugs can cause problems for people, the environment or a company. We'll draw important distinctions between defects, their root causes and their effects. We'll explain why testing is necessary to find these defects, how testing promotes quality, and how testing fits into quality assurance. In this section, we will also introduce some fundamental principles of testing. As we go through this section, watch for the Syllabus terms bug, defect, error, failure, fault, mistake, quality, risk, software, testing and exhaustive testing. You'll find these terms defined in the glossary.
- 4. Testing is done differently in different contexts. For example, safety-critical software istested differently from an e-commerce site. These days, almost everyone is aware of software systems.Some of the problems we encounter when using software are quite trivial,but others can be costly and damaging - with loss of money, time or businessreputation - and even may result in injury or death. For example, suppose auser interface has typographical defects. Does this matter? It may be trivial, butit could have a significant effect, depending on the website and the defect: If my personal family-tree website has my maternal grandmother's maidenname spelt wrong, my mother gets annoyed and I have to put up with somefamily teasing, but I can fix it easily and only the family see it (probably). If the company website has some spelling mistakes in the text, potential customers may be put off the company as it looks unprofessional. If a software program miscalculates pesticide application quantities, theeffect could be very significant: suppose a decimal point is wrongly placed sothat the application rate is 10 times too large. The farmer or gardener usesmore pesticide than needed, which raises his costs, has environmentalimpacts on wildlife and water supplies and has health and safety impact forthe farmer, gardener, family and workforce, livestock and pets. There mayalso be consequent loss of trust in and business for the company and possible legal costs and fines for causing the environmental and health problems. Software systems context
- 5. If someone makes an error or mistake in using the software, this may leaddirectly to a problem - the software is used incorrectly and so does not behaveas we expected. However, people also design and build the software and theycan make mistakes during the design and build. These mistakes mean that thereare flaws in the software itself. These are called defects or sometimes bugs orfaults. Remember, the software is not just the code; check the definition of soft-ware again to remind yourself. When the software code has been built, it is executed and then any defects maycause the system to fail to do what it should do (or do something it shouldn't),causing a failure. . Not all defects result in failures; some stay dormant in the codeand we may never notice them. Causes of software defects
- 6. ▪ errors in the specification, design and implementation of the software andsystem; 6 ▪ errors in use of the system; ▪ environmental conditions; ▪ intentional damage; When we think about what might go wrong we have to consider defects andfailures arising from: 1 2 3 4 5
- 7. Role of testing in software development, maintenance and operations We have seen that human errors can cause a defect or fault to be introduced atany stage within the software development life cycle and, depending upon theconsequences of the mistake, the results can be trivial or catastrophic. Testing and quality Testing helps us to measure the quality of software in terms of the number ofdefects found, the tests run, and the system covered by the tests. We can do thisfor both the functional attributes of the software (for example, printing a reportcorrectly) and for the non-functional software requirements and characteristics(for example, printing a report quickly enough). Testing can give confidence in the quality of the software if it finds few or no defects, provided we are happy that the testing is sufficiently rigorous . Of course, a poor test may uncover few defects and leave uswith a false sense of security. rigorous · adj. 1 extremely thorough, exhaustive, or accurate. 2 (of a rule, system, etc.) strictly applied or adhered to. Ø adhering strictly to a belief, opinion, or system. 3 (of weather) harsh. – DERIVATIVESrigorously adv. rigorousness n. – ORIGIN ME: from OFr. rigorous or late L. rigorosus, from rigor (see rigor1).
- 9. Projects aim to deliver software to specification. For the project to deliverwhat the customer needs requires a correct specification. Additionally, thedelivered system must meet the specification. This is known as validation ('isthis the right specification?') and verification ('is the system correct to specification?'). Of course, as well as wanting the right software system built correctly, the customer wants the project to be within budget and timescale – itshould arrive when they need it and not cost too much. The ISTQB glossary definition covers not just the specified requirements butalso user and customer needs and expectations. It is important that the projectteam, the customers and any other project stakeholders set and agree expectations. We need to understand what the customers understand by quality andwhat their expectations are. What we as software developers and testers maysee as quality – that the software meets its defined specification, is technicallyexcellent and has few bugs in it –may not provide a quality solution for our customers. Furthermore, if our customers find they have spent more money thanthey wanted or that the software doesn't help them carry out their tasks, theywon't be impressed by the technical excellence of the solution. If the customerwants a cheap car for a 'run-about' and has a small budget then an expensivesports car or a military tank are not quality solutions, however well built theyare.
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