Chapter 13 Software Testing...

Software Engineering: A Practitioner’s Approach, 6/eSoftware Engineering: A Practitioner’s Approach, 6/e

Chapter 13Chapter 13Software Testing StrategiesSoftware Testing Strategies

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

copyright © 1996, 2001, 2005

R.S. Pressman & Associates, Inc.

For University Use OnlyMay be reproduced ONLY for student use at the university level

when used in conjunction with Software Engineering: A Practitioner's Approach.Any other reproduction or use is expressly prohibited.

Software TestingSoftware Testing

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.


errors 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 Software?Who Tests the 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 it

and, 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 ‘testingtesting--inin--thethe--small’small’ and move toward and move toward ‘‘testingtesting--inin--thethe--large’large’

�� For conventional software:For conventional software:

�� The module (component) is our initial focusThe module (component) is our initial focus


�� The module (component) is our initial focusThe module (component) is our initial focus

�� Integration of modules followsIntegration of modules follows

�� For OO software:For OO software:

�� our focus when “testing in the small” changes from an our focus when “testing in the small” changes from an individual module (the conventional view) to an OO class individual module (the conventional view) to an OO class that encompasses attributes and operations and implies that encompasses attributes and operations and implies communication and collaborationcommunication and collaboration

Strategic IssuesStrategic Issues

�� State testing objectives explicitly. State testing objectives explicitly.

�� Understand the users of the software and develop a profile for Understand the users of the software and develop a profile for each user category.each user category.

�� Develop a testing plan that emphasizes “rapid cycle testing.”Develop a testing plan that emphasizes “rapid cycle testing.”

�� Build “robust” software that is designed to test itself.Build “robust” software that is designed to test itself.


�� Build “robust” software that is designed to test itself.Build “robust” software that is designed to test itself.

�� Use effective formal technical reviews as a filter prior to testing.Use effective formal technical reviews as a filter prior to testing.

�� Conduct formal technical reviews to assess the test strategy Conduct formal technical reviews to assess the test strategy and test cases themselves. and test cases themselves.

�� Develop a continuous improvement approach for the testing Develop a continuous improvement approach for the testing process. process.

Unit TestingUnit Testing

modulemoduleto beto be

testedtested


test casestest cases

resultsresults

softwaresoftwareengineerengineer

Unit TestingUnit Testing

interface interface

local data structureslocal data structures

boundary conditionsboundary conditions

modulemoduleto beto be

testedtested



independent pathsindependent paths

error handling pathserror handling paths


Unit Test EnvironmentUnit Test Environment

ModuleModule

driverdriver

interface interface

local data structureslocal data structures




stubstub stubstub

RESULTSRESULTS


error handling pathserror handling paths


Integration Testing StrategiesIntegration Testing Strategies

Options: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

AA

BB FF GG


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 resome subset of tests is re--runrun

CC

DD EE

BottomBottom--Up IntegrationUp Integration

drivers are replaced one at a drivers are replaced one at a

AA

BB FF GG


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

CC

DD EE

clustercluster

Sandwich TestingSandwich Testing

Top modules areTop modules aretested with stubstested with stubs

AA

BB FF GG


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

CC

DD EE

clustercluster

ObjectObject--Oriented TestingOriented Testing

�� Begins by evaluating the correctness and consistency of Begins by evaluating the correctness and consistency of the OOA and OOD modelsthe OOA and OOD models

�� Testing strategy changesTesting strategy changes

�� the concept of the ‘unit’ broadens due to encapsulationthe concept of the ‘unit’ broadens due to encapsulation


�� the concept of the ‘unit’ broadens due to encapsulationthe concept of the ‘unit’ broadens due to encapsulation

�� integration focuses on classes and their execution across a integration focuses on classes and their execution across a ‘thread’ or in the context of a usage scenario‘thread’ or in the context of a usage scenario

�� validation uses conventional black box methodsvalidation uses conventional black box methods

�� Test case design draws on conventional methods, but Test case design draws on conventional methods, but also encompasses special featuresalso encompasses special features

Broadening the View of “Testing”Broadening the View of “Testing”

It can be argued that the review of OO analysis and It can be argued that the review of OO analysis and

design models is especially useful because the design models is especially useful because the

same semantic constructs (e.g., classes, attributes, same semantic constructs (e.g., classes, attributes,

operations, messages) appear at the analysis, operations, messages) appear at the analysis,

design, and code level. Therefore, a problem in the design, and code level. Therefore, a problem in the


design, and code level. Therefore, a problem in the design, and code level. Therefore, a problem in the

definition of class attributes that is uncovered definition of class attributes that is uncovered

during analysis will circumvent side effects that during analysis will circumvent side effects that

might occur if the problem were not discovered might occur if the problem were not discovered

until design or code (or even the next iteration of until design or code (or even the next iteration of

analysis). analysis).

Testing the CRC ModelTesting the CRC Model

1. Revisit the CRC model and the object1. Revisit the CRC model and the object--relationship model.relationship model.

2. Inspect the description of each CRC index card to determine if 2. Inspect the description of each CRC index card to determine if a delegated responsibility is part of the collaborator’s definition.a delegated responsibility is part of the collaborator’s definition.

3. Invert the connection to ensure that each collaborator that is 3. Invert the connection to ensure that each collaborator that is asked for service is receiving requests from a reasonable source.asked for service is receiving requests from a reasonable source.

4. Using the inverted connections examined in step 3, determine 4. Using the inverted connections examined in step 3, determine


4. Using the inverted connections examined in step 3, determine 4. Using the inverted connections examined in step 3, determine whether other classes might be required or whether whether other classes might be required or whether responsibilities are properly grouped among the classes.responsibilities are properly grouped among the classes.

5. Determine whether widely requested responsibilities might be 5. Determine whether widely requested responsibilities might be combined into a single responsibility.combined into a single responsibility.

6. Steps 1 to 5 are applied iteratively to each class and through 6. Steps 1 to 5 are applied iteratively to each class and through each evolution of the OOA model.each evolution of the OOA model.

OOT StrategyOOT Strategy

�� Class testing is the equivalent of unit testing:Class testing is the equivalent of unit testing:

�� operations within the class are testedoperations within the class are tested

�� the state behavior of the class is examinedthe state behavior of the class is examined

�� Integration applies three different strategies:Integration applies three different strategies:


�� threadthread--based testingbased testing——integrates the set of classes integrates the set of classes required to respond to one input or eventrequired to respond to one input or event

�� useuse--based testingbased testing——integrates the set of classes required integrates the set of classes required to respond to one use caseto respond to one use case

�� cluster testingcluster testing——integrates the set of classes required to integrates the set of classes required to demonstrate one collaborationdemonstrate one collaboration

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.


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


�� 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 runtest the run--time performance of software within the context of an 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 conduct


causecauseand conductand conductregression testsregression tests

Symptoms & CausesSymptoms & Causes

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 noncombination of non--errors errors


symptomsymptomcausecause

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

seriousserious

extremeextremecatastrophiccatastrophic

infectiousinfectious


mildmildannoyingannoying

disturbingdisturbingseriousserious

Bug TypeBug Type

Bug Categories:Bug Categories: functionfunction--related bugs, related bugs, systemsystem--related bugs, data bugs, coding bugs, 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 ThoughtsDebugging: Final Thoughts

Don't run off halfDon't run off half--cocked, 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.

1.1.

2.2.


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 testswhen you do "fix" the bug.when you do "fix" the bug.

3.3.

4.4.

Chapter 13 Software Testing...

Documents

Transcript of Chapter 13 Software Testing...