these courseware materials are to be used in conjunction with

These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 1

Chapter 13Chapter 13Software Testing Software Testing

StrategiesStrategies


Software Software TestingTesting

Testing is the process of exercising aTesting is the process of exercising aprogram with the specific intent of findingprogram with the specific intent of findingerrors prior to delivery to the end user.errors prior to delivery to the end user.


What Testing ShowsWhat Testing Shows

errorserrors

requirements conformancerequirements conformance

performanceperformance

an indicationan indicationof qualityof quality


Who Tests the Who Tests the Software?Software?

developerdeveloper independent testerindependent tester

Understands the system Understands the system

but, will test "gently"but, will test "gently"

and, is driven by "delivery"and, is driven by "delivery"

Must learn about the system,Must learn about the system,but, will attempt to break itbut, will attempt to break itand, is driven by qualityand, is driven by quality


Testing StrategyTesting Strategy

unit testunit test integrationintegrationtesttest

validationvalidationtesttest

systemsystemtesttest


Testing StrategyTesting Strategy

We begin by ‘We begin by ‘testing-in-the-small’testing-in-the-small’ and move and move toward ‘toward ‘testing-in-the-large’testing-in-the-large’

For conventional softwareFor conventional software The module (component) is our initial focusThe module (component) is our initial focus Integration of modules followsIntegration of modules follows


Strategic IssuesStrategic Issues

State testing objectives explicitly. State testing objectives explicitly. Understand the users of the software and Understand the users of the software and

develop a profile for each user category.develop a profile for each user category. Build “robust” software that is designed to test Build “robust” software that is designed to test

itselfitself Use effective formal technical reviews as a filter Use effective formal technical reviews as a filter

prior to testingprior to testing Conduct formal technical reviews to assess the Conduct formal technical reviews to assess the

test strategy and test cases themselves. test strategy and test cases themselves. Develop a continuous improvement approach for Develop a continuous improvement approach for

the testing process. the testing process.


Unit TestingUnit Testing

modulemoduleto beto betestedtested

test casestest cases

resultsresults

softwaresoftwareengineerengineer


Unit TestingUnit Testing

interface interface local data structureslocal data structures

boundary conditionsboundary conditionsindependent pathsindependent pathserror handling pathserror handling paths

modulemoduleto beto betestedtested



Unit Test Unit Test EnvironmentEnvironment

ModuleModule

stubstub stubstub

driverdriver

RESULTSRESULTS

interface interface

local data structureslocal data structures

boundary conditionsboundary conditions

independent pathsindependent paths

error handling pathserror handling paths



Integration Testing StrategiesIntegration Testing StrategiesOptions:Options:

•• the “big bang” approachthe “big bang” approach•• an incremental construction strategyan incremental construction strategy


Top Down IntegrationTop Down Integration

top module is tested with top module is tested with stubsstubs

stubs are replaced one at stubs are replaced one at a time, "depth first"a time, "depth first"

as new modules are integrated, as new modules are integrated, some subset of tests is re-runsome subset of tests is re-run

AA

BB

CC

DD EE

FF GG


Bottom-Up IntegrationBottom-Up Integration

drivers are replaced one at a drivers are replaced one at a time, "depth first"time, "depth first"

worker modules are grouped into worker modules are grouped into builds and integratedbuilds and integrated

AA

BB

CC

DD EE

FF GG

clustercluster


Sandwich TestingSandwich Testing

Top modules areTop modules aretested with stubstested with stubs

Worker modules are grouped into Worker modules are grouped into builds and integratedbuilds and integrated

AA

BB

CC

DD EE

FF GG

clustercluster


Smoke TestingSmoke Testing A common approach for creating “daily builds” for product A common approach for creating “daily builds” for product

softwaresoftware Smoke testing steps:Smoke testing steps:

Software components that have been translated into code are Software components that have been translated into code are integrated into a “build.” integrated into a “build.”

A build includes all data files, libraries, reusable modules, and A build includes all data files, libraries, reusable modules, and engineered components that are required to implement one or engineered components that are required to implement one or more product functions.more product functions.

A series of tests is designed to expose errors that will keep A series of tests is designed to expose errors that will keep the build from properly performing its function. the build from properly performing its function.

The intent should be to uncover “show stopper” errors that have The intent should be to uncover “show stopper” errors that have the highest likelihood of throwing the software project behind the highest likelihood of throwing the software project behind schedule.schedule.

The build is integrated with other builds and the entire The build is integrated with other builds and the entire product (in its current form) is smoke tested daily. product (in its current form) is smoke tested daily.

The integration approach may be top down or bottom up.The integration approach may be top down or bottom up.


High Order TestingHigh Order Testing Validation testingValidation testing

Focus is on software requirementsFocus is on software requirements System testingSystem testing

Focus is on system integrationFocus is on system integration Alpha/Beta testingAlpha/Beta testing

Focus is on customer usageFocus is on customer usage Recovery testingRecovery testing

forces the software to fail in a variety of ways and verifies that forces the software to fail in a variety of ways and verifies that recovery is properly performedrecovery is properly performed

Security testingSecurity testing verifies that protection mechanisms built into a system will, in fact, verifies that protection mechanisms built into a system will, in fact,

protect it from improper penetrationprotect it from improper penetration Stress testingStress testing

executes a system in a manner that demands resources in abnormal executes a system in a manner that demands resources in abnormal quantity, frequency, or volumequantity, frequency, or volume

Performance TestingPerformance Testing test the run-time performance of software within the context of an test the run-time performance of software within the context of an

integrated systemintegrated system


Debugging: Debugging: A Diagnostic ProcessA Diagnostic Process


The Debugging ProcessThe Debugging Processtest casestest cases

resultsresults

DebuggingDebugging

suspectedsuspectedcausescauses

identifiedidentifiedcausescauses

correctionscorrections

regressionregressionteststests

new testnew testcasescases


Debugging EffortDebugging Effort

time requiredtime requiredto diagnose theto diagnose thesymptom andsymptom anddetermine thedetermine thecausecause

time requiredtime requiredto correct the errorto correct the errorand conductand conductregression testsregression tests


Symptoms & CausesSymptoms & Causes

symptomsymptomcausecause

symptom and cause may be symptom and cause may be geographically separated geographically separated

symptom may disappear when symptom may disappear when another problem is fixedanother problem is fixed

cause may be due to a cause may be due to a combination of non-errors combination of non-errors

cause may be due to a system cause may be due to a system or compiler erroror compiler error

cause may be due to cause may be due to assumptions that everyone assumptions that everyone believesbelieves

symptom may be intermittentsymptom may be intermittent


Consequences of BugsConsequences of Bugs

damagedamage

mildmild annoyingannoying

disturbingdisturbingseriousserious

extremeextremecatastrophiccatastrophic

infectiousinfectious

Bug TypeBug Type

Bug Categories:Bug Categories: function-related bugs, function-related bugs, system-related bugs, data bugs, coding bugs, system-related bugs, data bugs, coding bugs, design bugs, documentation bugs, standards design bugs, documentation bugs, standards violations, etc.violations, etc.


Debugging TechniquesDebugging Techniques

brute force / testingbrute force / testing

backtrackingbacktracking

inductioninduction

deductiondeduction


Debugging: Final Debugging: Final ThoughtsThoughts

Don't run off half-cocked, Don't run off half-cocked, thinkthink about the about the symptom you're seeing.symptom you're seeing.

Use toolsUse tools (e.g., dynamic debugger) to gain (e.g., dynamic debugger) to gain more insight.more insight.

If at an impasse, If at an impasse, get helpget help from someone else.from someone else.

Be absolutely sure to Be absolutely sure to conduct regression testsconduct regression tests when you do "fix" the bug.when you do "fix" the bug.

1.1.

2.2.

3.3.

4.4.


Chapter 14Chapter 14Software Testing Software Testing

TechniquesTechniques


TestabiliTestabilityty OperabilityOperability—it operates cleanly—it operates cleanly

ObservabilityObservability—the results of each test case are —the results of each test case are readily observedreadily observed

ControllabilityControllability—the degree to which testing can —the degree to which testing can be automated and optimizedbe automated and optimized

DecomposabilityDecomposability—testing can be targeted—testing can be targeted SimplicitySimplicity—reduce complex architecture and —reduce complex architecture and

logic to simplify testslogic to simplify tests StabilityStability—few changes are requested during —few changes are requested during

testingtesting UnderstandabilityUnderstandability—of the design—of the design


What is a “Good” Test?What is a “Good” Test?

A good test has a high probability of A good test has a high probability of finding an errorfinding an error

A good test is not redundant.A good test is not redundant. A good test should be “best of breed” A good test should be “best of breed” A good test should be neither too A good test should be neither too

simple nor too complexsimple nor too complex


Test Case Test Case DesignDesign

"Bugs lurk in corners "Bugs lurk in corners and congregate at and congregate at boundaries ..."boundaries ..."

Boris BeizerBoris Beizer

OBJECTIVEOBJECTIVE

CRITERIACRITERIA

CONSTRAINTCONSTRAINT

to uncover errorsto uncover errors

in a complete mannerin a complete manner

with a minimum of effort and timewith a minimum of effort and time


Exhaustive TestingExhaustive Testing

loop < 20 Xloop < 20 X

There are 10 possible paths! If we execute oneThere are 10 possible paths! If we execute onetest per millisecond, it would take 3,170 years totest per millisecond, it would take 3,170 years totest this program!!test this program!!

1414


Selective TestingSelective Testing

loop < 20 Xloop < 20 X

Selected pathSelected path


Software TestingSoftware Testing

Methods

Strategies

white-boxmethods

black-box methods


White-Box White-Box TestingTesting

... our goal is to ensure that all ... our goal is to ensure that all statements and conditions have statements and conditions have been executed at least once ...been executed at least once ...


Why Why Cover?Cover?

logic errors and incorrect assumptions logic errors and incorrect assumptions are inversely proportional to a path's are inversely proportional to a path's execution probabilityexecution probability

we often we often believebelieve that a path is not that a path is not likely to be executed; in fact, reality is likely to be executed; in fact, reality is often counter intuitiveoften counter intuitive

typographical errors are random; it's typographical errors are random; it's likely that untested paths will contain likely that untested paths will contain some some


Basis Path Basis Path TestingTesting

First, we compute the cyclomatic complexity:

number of simple decisions + 1

or

number of enclosed areas + 1

In this case, V(G) = 4


Cyclomatic Cyclomatic ComplexityComplexityA number of industry studies have indicated A number of industry studies have indicated

that the higher V(G), the higher the probability that the higher V(G), the higher the probability or errors.or errors.

V(G)V(G)

modulesmodules

modules in this range are modules in this range are more error pronemore error prone


Basis Path Basis Path TestingTestingNext, we derive the Next, we derive the

independent paths:independent paths:

Since V(G) = 4,Since V(G) = 4,there are four pathsthere are four paths

Path 1: 1,2,3,6,7,8Path 1: 1,2,3,6,7,8Path 2: 1,2,3,5,7,8Path 2: 1,2,3,5,7,8Path 3: 1,2,4,7,8Path 3: 1,2,4,7,8Path 4: 1,2,4,7,2,4,...7,8Path 4: 1,2,4,7,2,4,...7,8

Finally, we derive testFinally, we derive testcases to exercise these cases to exercise these paths.paths.

11

22

3344

55 66

77

88


Basis Path Testing Basis Path Testing NotesNotesyou don't need a flow chart, you don't need a flow chart, but the picture will help when but the picture will help when you trace program pathsyou trace program paths

count each simple logical test, count each simple logical test, compound tests count as 2 or compound tests count as 2 or moremore

basis path testing should be basis path testing should be applied to critical modulesapplied to critical modules


Graph MatricesGraph Matrices A graph matrix is a square matrix whose size A graph matrix is a square matrix whose size

(i.e., number of rows and columns) is equal (i.e., number of rows and columns) is equal to the number of nodes on a flow graphto the number of nodes on a flow graph

Each row and column corresponds to an Each row and column corresponds to an identified node, and matrix entries identified node, and matrix entries correspond to connections (an edge) correspond to connections (an edge) between nodes. between nodes.

By adding a By adding a link weightlink weight to each matrix entry, to each matrix entry, the graph matrix can become a powerful tool the graph matrix can become a powerful tool for evaluating program control structure for evaluating program control structure during testingduring testing


Control Structure TestingControl Structure Testing

Condition testingCondition testing — a test case design method — a test case design method that exercises the logical conditions contained in that exercises the logical conditions contained in a program modulea program module

Data flow testingData flow testing — selects test paths of a — selects test paths of a program according to the locations of definitions program according to the locations of definitions and uses of variables in the programand uses of variables in the program


Loop TestingLoop Testing

Nested Nested LoopsLoops

ConcatenatedConcatenated Loops Loops Unstructured Unstructured

LoopsLoops

Simple Simple looploop


Loop Testing: Simple Loop Testing: Simple LoopsLoops

Minimum conditions—Simple LoopsMinimum conditions—Simple Loops

1. skip the loop entirely1. skip the loop entirely

2. only one pass through the loop2. only one pass through the loop3. two passes through the loop3. two passes through the loop4. m passes through the loop m < n4. m passes through the loop m < n5. (n-1), n, and (n+1) passes through 5. (n-1), n, and (n+1) passes through the loopthe loop

where n is the maximum number where n is the maximum number of allowable passesof allowable passes


Loop Testing: Nested Loop Testing: Nested LoopsLoops

Start at the innermost loop. Set all outer loops to their Start at the innermost loop. Set all outer loops to their minimum iteration parameter values.minimum iteration parameter values.

Test the min+1, typical, max-1 and max for the Test the min+1, typical, max-1 and max for the innermost loop, while holding the outer loops at their innermost loop, while holding the outer loops at their minimum values.minimum values.Move out one loop and set it up as in step 2, holding all Move out one loop and set it up as in step 2, holding all other loops at typical values. Continue this step until other loops at typical values. Continue this step until the outermost loop has been tested.the outermost loop has been tested.

If the loops are independent of one another If the loops are independent of one another then treat each as a simple loopthen treat each as a simple loop else* treat as nested loopselse* treat as nested loopsendif* endif*

for example, the final loop counter value of loop 1 is for example, the final loop counter value of loop 1 is used to initialize loop 2.used to initialize loop 2.

Nested LoopsNested Loops

Concatenated LoopsConcatenated Loops


Black-Box TestingBlack-Box Testing

requirementsrequirements

eventseventsinputinput

outputoutput


Black-Box TestingBlack-Box Testing How is functional validity tested?How is functional validity tested? How is system behavior and performance tested?How is system behavior and performance tested? What classes of input will make good test cases?What classes of input will make good test cases? Is the system particularly sensitive to certain Is the system particularly sensitive to certain

input values?input values? How are the boundaries of a data class isolated?How are the boundaries of a data class isolated? What data rates and data volume can the system What data rates and data volume can the system

tolerate?tolerate? What effect will specific combinations of data What effect will specific combinations of data

have on system operation?have on system operation?


Graph-Based MethodsGraph-Based Methods

newfile

menu select generates

(generation time 1.0 sec)document

window

documenttex

t

is represented as

contains

Attributes:

background color: whitetext color: default color

or preferences

(b)

object#1

Directed link

(link weight)object

#2

object#3

Undirected link

Parallel links

Node weight(value

)

(a)

allows editingof

To understand To understand the objects that the objects that are modeled in are modeled in software and software and the the relationships relationships that connect that connect these objectsthese objects

In this context, we In this context, we consider the term consider the term “objects” in the “objects” in the broadest possible broadest possible context. It context. It encompasses data encompasses data objects, traditional objects, traditional components components (modules), and (modules), and object-oriented object-oriented elements of elements of computer software.computer software.


Equivalence PartitioningEquivalence Partitioning

useruserqueriesqueries

mousemousepickspicks

outputoutputformatsformats

promptsprompts

FKFKinputinput

datadata


Sample Equivalence Sample Equivalence ClassesClasses

user supplied commandsuser supplied commandsresponses to system promptsresponses to system promptsfile namesfile namescomputational datacomputational data physical parameters physical parameters bounding valuesbounding values initiation valuesinitiation valuesoutput data formattingoutput data formattingresponses to error messagesresponses to error messagesgraphical data (e.g., mouse picks)graphical data (e.g., mouse picks)

data outside bounds of the program data outside bounds of the program physically impossible dataphysically impossible dataproper value supplied in wrong placeproper value supplied in wrong place

Valid dataValid data

Invalid dataInvalid data


Boundary Value Boundary Value AnalysisAnalysis

useruserqueriesqueries

mousemousepickspicks

outputoutputformatsformats

promptsprompts

FKFKinputinput

datadata

outputoutputdomaindomaininput domaininput domain


Comparison TestingComparison Testing

Used only in situations in which the reliability of Used only in situations in which the reliability of software is absolutely critical (e.g., human-rated software is absolutely critical (e.g., human-rated systems)systems) Separate software engineering teams develop Separate software engineering teams develop

independent versions of an application using the same independent versions of an application using the same specificationspecification

Each version can be tested with the same test data to Each version can be tested with the same test data to ensure that all provide identical output ensure that all provide identical output

Then all versions are executed in parallel with real-time Then all versions are executed in parallel with real-time comparison of results to ensure consistencycomparison of results to ensure consistency


Orthogonal Array TestingOrthogonal Array Testing Used when the number of input parameters is

small and the values that each of the parameters may take are clearly bounded

One input item at a time L9 orthogonal array

XY

Z

XY

Z

these courseware materials are to be used in conjunction with

Documents

software testing testing

testing process

security testing

testing understandability

sandwich testing

software testing techniques

software testing strategies

unit testing module