Testing Ch 9

7/31/2019 Testing Ch 9

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TESTING



NEED OF TESTING

• The aim of program testing is to identify alldefects in a program.

• Software testing is needed to verify and validate

that the software that has been built to meet thespecifications.

• Testing ensures that what you get in the end iswhat you wanted to build.

• Testing enhances the integrity of a system bydetecting deviations in design and errors in thesystem.



Basic concepts

• Testing a program involves providing the program withset of test inputs and observing the program behavesas expected.

• An error is a mistake commited by the development

team during development phase.(a fault, a bug, adefect)

• A test case is a triplet[I,S,O]

• A test suite is the set of all test cases with which a

given software tested.• While verification is concerned with phase

containment of errors, the aim of validation is to makefinal product error free.



Levels of testing



1)Unit testing:

• It is referred as testing in the small.

• Unit testing is undertaken after a module has been codedand reviewed.

• During unit testing, all the individual components of a

program are tested .• Requires knowledge of the internal program design and

code.

• Done by Programmers (not by testers).

Methods for testing are White Box testing techniques,TestCoverage techniques

.



2)Integration testing:

• After testing individually, the units are slowly

integrated and tested after each step of

integration

• Developers does this type of testing.

• Methods of testing are: White and Black Box

techniques



3)System testing:

Finally, the fully integrated system is tested.

Integration testing and system testing are known

as testing in the large.

• Objective is To perform inter-system test and

to check the transaction flow

•

To demonstrate that the system performs bothfunctionally and operationally as specified

System testers do this kind of test.



4) Systems Integration Testing

• To test the co-existence of products and

applications that are required to perform

together in the production-like operational

environment

• The system connected with the network in

organisation and make an environment where

the project can be run and test it

• System Testers do this kind of test.



5) Acceptance Testing

• The objective is To verify that the system

meets the user requirements

• It is done in the users environment

• User does this kind of testing



Testing methods/techniques



1)Black box testing:

This testing methodology looks at what are the

available inputs for an application and what

the expected outputs are that should result

from each input.

• It is solely based on an analysis of the

input/output behaviour(functional behaviour)

• This testing is also known as functional testing



2)White box testing:

white-box testing enables you to see what is

happening inside the application.

• It means while designing test cases for white

box testing ,one needs to have a thorough

knowledge of the internal structure of a

program.

• It is also known as structural testing.

• It is based on analysis of the code.



Testing activities



code

Design

document

SRS

document

Design test

suite Test suite

Run testand

check

result

Failure list

Debug

programError listCorrected

errors

Corrected

programs



Design test cases



Design test cases In Black box testing

• There are two approaches to design black box testcases

1)Equivalence class partitioning

Here the domain of input values to the program under

test is partitioned into a set of equivalence classes andtake one input from each class to form test case

General guidelines for designing the equivalence classes:

-if the range of values specified in the program, then one

valid and two invalid classes need to be identified.--if the input data assumes values from set of discrete

members of some domain, then one valid class andone invalid class should be defined.(eg, ABCD)



2)Boundary value analysis:

Boundary value analysis-based test suite design

involves designing test cases using the valuesat the boundaries of different equivalnceclasses.

It is done to find out the error related to the

<;>;>=;<= etc.

Here first the equivalence classes is identifiedonly if it contains range of values. And

boundary values are included in the test case.If there are not a range of values ,then boundary

value test case can’t be defined.



problem

1)For software that computes the square root

of an integer that can assume values in the

range of 0 to 5000. determine the equivance

and boundary value analysis

2)Design equivalence class for a function that

reads a character string of size less than five

characters and displays whether it ispalindrome.



Design test cases In White box testing

• Large no. of white box testing strategies exists

to design test cases.

• Each strategies design test cases based on the

analysis of source code.

• Ex:

1)statement coverage strategy

2)branch coverage strategy

3)path coverage



Statement coverage strategy

• It aims to design test cases so as to execute

every statement in a program at least once.

• Here for upper control loop, it needs to be

false. And for inner control loop, it needs to be

made true and false.



Branch coverage strategies

• It aims at designing test cases so as to make

each branch condition in a program to assume

true and false values in turn.

• It is stronger testing than statement coverage

testing



Path coverage strategy

• It aims at designing test cases such that alllinearly independent paths(basis path) In theprogram are executed at least once.

• Before identifying the basis path, tester needto have the knowledge of CFG

• CFG is a control flow graph. It describes how

the control flows trough the program.• CFG for sequence, selection and iteration.

• Specify the nodes and edge in the CFG.



• Find the no of linear independent graph in theprogram using Mccabe’s Cyclomatic complexity

metricV(G)=E-N+2

• Then find out the path from source to destination.

each path should be different from others.meanssame nodes should not be in other path.inaddition new node should be there.

And specific value is given according to path

Example:path1= (1,6) value=(3,3)



Debugging approches

After a failure has been detected, it is necessary tofirst identify the program statements that are inerror and are responsible for the failure, the errorcan then be fixed.

Approaches:1)backtracking:

fairly common approach

in this approach, beginning from the statement atwhich an error symptom has been observed, thesource code is traced backwards until the error isdiscovered.



2)Cause elimination method:

In this approach, once a failure is observed, the

symptoms of the failure(that is certain

variable is having a –ve value though it should

be +ve, etc) are noted.

After it, the cause of error is found and it is

corrected.



Code reviews

• Code review is undertaken after the modulesuccessfully compiles.

• Reviews directly detect errors while testing is

done stepwise. Failure finding is the result of testing. hence it is effective.

• There are two types of reviews are carried out

on the code of the module.1)Code walkthrough

2)Code inspection



• Code walkthrough:

The main aim of this is to discover the

algorithmic and logical errors in the code.

• Code inspection:

The main aim of this is to check for the presense

of some common type errors that usually due

to programmer oversights and to check

whether coding standards have been adhered

to.



Stress test

• the goals of such tests may be to ensure the softwaredoes not crash in conditions of insufficient computational resources (such as memory or diskspace)

•

Stress testing tries to break the system under test• Stress testing evaluates system performance when it is

stressed for short periods times.

• For eg. Imposing a range of illegal input condition so asto stress the capabilities of the software.

• Input data volume,input data rate,processing time,utiliation of memory etc are tested beyond thedesigned capacity.

http://en.wikipedia.org/wiki/Crash_(computing)


http://en.wikipedia.org/wiki/Random_access_memory


http://en.wikipedia.org/wiki/Disk_storage








Load test

• "load testing" is usually defined as the

process of exercising the system under test by

feeding it the largest tasks it can operate with.

• load testing operates at a predefined load

level, usually the highest load that the system

can accept while still functioning properly.



Use case based testing

• For each use case typically consists of a

mainline scenario and severalalternate

scenarios.

• The mainline and alternate sequences are

covered to check if any errors show up.



automation testing

• .Test automation is the process of writing a computer program todo testing

• This is often the most cost effective method for software products

• There are two general approaches to test automation:

1)Code-driven testing. The public (usually) interfaces to classes,

modules, or libraries are tested with a variety of input arguments tovalidate that the results that are returned are correct.

2)Graphical user interface testing. A testing framework generates userinterface events such as keystrokes and mouse clicks, and observesthe changes that result in the user interface, to validate that theobservable behavior of the program is correct.

http://en.wikipedia.org/wiki/Public_interface

http://en.wikipedia.org/wiki/Graphical_user_interface

http://en.wikipedia.org/wiki/Graphical_user_interface

http://en.wikipedia.org/wiki/Public_interface



Integration testing

• The primary objective of this testing is to test themodule interfaces, i.e. there are no errors inparameter passing, when one module invokes thefunctionality of another module.

• Four approaches:

1)big-bang integration testing

2)Bottom up

3)Top down

4)Mixed

Documents

Testing Ch 9