Fundamentals of testing

FUNDAMENTALS OF TESTING
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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.

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.

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

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

▪ 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

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).

 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.

Fundamentals of testing

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Fundamentals of testing