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Regardless of the limitations, testing is an integral part in software development. It is broadly deployed in every phase in the software development cycle. Typically, more than 50% percent of the development time is spent in testing. Testing is usually performed for the following purposes:

To improve quality

As computers and software are used in critical applications, the outcome of a bug can be severe. Bugs can cause huge losses. Bugs in critical systems have caused airplane crashes, allowed space shuttle missions to go awry, halted trading on the stock market, and worse. Bugs can kill. Bugs can cause disasters. In a computerized embedded world, the quality and reliability of software is a matter of life and death.

Quality means the conformance to the specified design requirement. Being correct, the minimum requirement of quality, means performing as required under specified circumstances. Debugging, a narrow view of software testing, is performed heavily to find out design defects by the programmer. The imperfection of human nature makes it almost impossible to make a moderately complex program correct the first time. Finding the problems and get them fixed, is the purpose of debugging in programming phase.

For verification&Validation (v&V)

An important purpose of testing is verification and validation. Testing can serve as metrics. It is heavily used as a tool in the V&V process. Testers can make claims based on interpretations of the testing results, which either the product works under certain situations, or it does not work. We can also compare the quality among different products under the same specification, based on results from the same test.

We can not test quality directly, but we can test related factors to make quality visible. Quality has three sets of factors: functionality, engineering, and adaptability. These three sets of factors can be thought of as dimensions in the software quality space. Each dimension may be broken down into its component factors and considerations at successively lower levels of detail. Table 1 illustrates some of the most frequently cited quality considerations.

Functionality(exterior quality) Engineering(interior quality) Adaptability(future quality)
Correctness Efficiency Flexibility
Reliability Testability Reusability
Usability Documentation Maintainability
Integrity Structure
Table 1.  Typical Software Quality Factors 

Good testing provides measures for all relevant factors. The importance of any particular factor varies from application to application. Any system where human lives are at stake must place extreme emphasis on  reliability and integrity. In the typical business system usability and maintainability are the key factors, while for a one-time scientific program neither may be significant. Our testing, to be fully effective, must be geared to measuring each relevant factor and thus forcing quality to become tangible and visible.

Tests with the purpose of validating the product works are named clean tests, or positive tests. The drawbacks are that it can only validate that the software works for the specified test cases. A finite number of tests can not validate that the software works for all situations. On the contrary, only one failed test is sufficient enough to show that the software does not work. Dirty tests, or negative tests, refers to the tests aiming at breaking the software, or showing that it does not work. A piece of software must have sufficient exception handling capabilities to survive a significant level of dirty tests.

Questions & Answers

short note on software engineering
prachi Reply
am interested
marvellous
Explain human computer interaction
amjad
AI
Louis
Human computer interaction is the study of how people interact with computers and to what extent computers are or are not developed for successful interaction with human beings. 
Hemant
human needs for the computer[stated]
Louis
AI=Artificial Intelligence
Louis
all explained abstractingly
Louis
Please give me a Standard definition of the word *software*
marvellous
what is sowftware?
rana Reply
please correct the spellings of software
majid
kk
Amissah
software engineering eligiblelity criteria for DAE civil students?
Engr Reply
what is software?
Abdullahi Reply
software means instructions or data that enable computers to work
majid
hi
Abdullahi
majid
Abdullahi
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majid
how you
Abdullahi
i want to be software engineer ing
Abdullahi
I am fine
majid
can i get more information about data structured centered design
Samir Reply
what is best course to get job
Eswar Reply
engineering
Abdullahi
Why do most computer sciences emphasize the technical foundations of software development?
Profneil Reply
The simplist model of software development paradigms all the phace of software development life cycle will functional one after another in linear manner. * When the phase is finish then only the second face will start.
udara Reply
yes
dawit
yes
Abdullahi
the reason for learning this course?
Gabriel Reply
what is soo muchh tough to understand in so software engineering?
Syed
yes
dawit
plz tell me waterfall model
Shantanu
j
Sobuj
components of software engineering
khan Reply
what is coding
YUSUF Reply
Coding is a type of a language that a computer understand..
HANAN
it's how a computer interprets software, programs and what to do when it reads the code. Code is like our sub-conscious but to a computer if that makes sense.
Dustin
hello, I don't know anything about software but I have this passion to learn. where do I start from pls
Oliver Reply
computer science class or just take a introduction to computers class. You can always try to find a mentor or self teach yourself as well.
Dustin
What is coding
diwakar
hgg
Sarik
what important of software
Tom Reply
dorimon in hindi
Yogesh
Hello
Mark
Mrs dorimon
Mark
hello
Tom
ha
Khizer
I'm. new in programming
Khizer
did anyone help
Khizer
me
Khizer
ok on me am new in programming
Tom
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Khizer
hello guy's
Shey
what can helps new in programming
Tom
I want to know more about programming
Shey
hello
Francis
hello
Xotambek
hi
Peterson
how r u my friends ?
Xotambek
l would like to know what do I need if I want to.create a sun glasses where you can see everything when you're sharing something via bluetooth
Peterson
hi
Peterson
I have so many things that I want to create in the technology industry
Peterson
but I need a group of people who are willing bring ideas on the table and work together to make success
Peterson
wow
Shey
What sorts of feild knowledge do you need?
leo
Mr. Peteson pinchinat, hello!
leo
I don't really know what do I need to learn that's why I'm asking
Peterson
I need help to create all those things that I want to.
Peterson
peterson pinchinat I have so many ideas and much more things in my mind
Khizer
hello
Purity
even Me guys
Mark
if you have many ideas than I have so let's work together let's build a team . let's put our ideas and start working together to make success.
Peterson
I really like to work with software
Khizer
any I like that people how have interest on new technology and software developer, engineering
Khizer
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Peterson
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Peterson
so where we can do work
Khizer
we have to find a way. I'm living in Brooklyn what about you?
Peterson
there we shared work
Khizer
I know people from India they are really good in compute
Peterson
thanks
Khizer
first we need to find out how we gonna work. I know the distance won't be a problem we need to trust each other and create a great team then bring revolution in the technology
Peterson
I have an idea
Khizer
ok
Peterson
send me the website?
Peterson
wait for a 2 days I make that and tell you ok
Khizer
perfect
Peterson
good
Shey
Yes ,It is possible to be a programmer without University Degree.You have a lot professional courses that you access and register for on the net.Please get hook and search ..thanks
NICCK-PAT
Great ,I am NICCk-PAT in Paris France.
NICCK-PAT
hello
Dustin
how do i create software
Ahmad Reply
Hii
Sameer
I am fine
Sarik
I am big bro this site and software engineering..?
Vikki
Any question guys?
Vikki
how to get grip on any programming language starting from scratch
Pavan
because iam new to programming
Pavan
sup
Louis
with your imagination for the love of computers
Louis
what is the IEEE ?
Shankar Reply
a external device cable capable of transferring large amounts of data at high speed.
Dustin
really
Shey

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Source:  OpenStax, Software engineering. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10790/1.1
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