Chapter 13 Software Testing Strategies - Aalborg...

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

Chapter 13Chapter 13Software Testing StrategiesSoftware Testing Strategies

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.


What Testing ShowsWhat Testing Shows

errorserrorsrequirements conformancerequirements conformance

performanceperformance

an indicationan indicationof qualityof quality


Who Tests the Software?Who Tests the Software?

developerdeveloper independent testerindependent testerUnderstands 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 Strategyunit testunit test integrationintegration

testtest

validationvalidationtesttest

systemsystemtesttest

V ModelV Model


Testing StrategyTesting Strategy

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

For OO softwareFor OO software our focus when our focus when ““testing in the smalltesting in the small”” changes from an changes from an

individual module (the conventional view) to an OO class thatindividual module (the conventional view) to an OO class thatencompasses attributes and operations and impliesencompasses attributes and operations and impliescommunication 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 each user category.Understand the users of the software and develop a profile for each user category. Develop a testing plan that emphasizes Develop a testing plan that emphasizes ““rapid cycle testing.rapid cycle testing.”” Build Build ““robustrobust”” software that is designed to test itself software that is designed to test itself Use effective formal technical reviews as a filter prior to testingUse effective formal technical reviews as a filter prior to testing Conduct formal technical reviews to assess the test strategy and test casesConduct formal technical reviews to assess the test strategy and test cases

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


Unit TestingUnit Testing

modulemoduleto beto be

testedtested

test casestest cases

resultsresults

softwaresoftwareengineerengineer


Unit TestingUnit Testing

interface interface local data structureslocal data structuresboundary conditionsboundary conditionsindependent pathsindependent pathserror handling pathserror handling paths

modulemoduleto beto be

testedtested



Unit Test EnvironmentUnit Test Environment

ModuleModule

stubstub stubstub

driverdriver

RESULTSRESULTS

interface interface local data structureslocal data structuresboundary conditionsboundary conditionsindependent pathsindependent pathserror handling pathserror handling paths



Integration Testing StrategiesIntegration Testing StrategiesOptions:Options:

•• the the ““big bangbig bang”” approach 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


Object-Oriented TestingObject-Oriented Testing

begins by evaluating the correctness and consistency ofbegins by evaluating the correctness and consistency ofthe OOA and OOD modelsthe OOA and OOD models

testing strategy changestesting strategy changes the concept of the the concept of the ‘‘unitunit’’ broadens due to encapsulation broadens due to encapsulation integration focuses on classes and their execution across aintegration focuses on classes and their execution across a

‘‘threadthread’’ or in the context of a usage scenario 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, buttest case design draws on conventional methods, butalso encompasses special featuresalso encompasses special features


Broadening the View of Broadening the View of ““TestingTesting””

It can be argued that the review of OO analysisIt can be argued that the review of OO analysisand design models is especially useful because theand design models is especially useful because thesame 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 thedesign, and code level. Therefore, a problem in thedefinition of class attributes that is uncovereddefinition of class attributes that is uncoveredduring analysis will circumvent side effects thatduring analysis will circumvent side effects thatmight occur if the problem were not discoveredmight occur if the problem were not discovereduntil design or code (or even the next iteration ofuntil design or code (or even the next iteration ofanalysis).analysis).


Testing the CRC ModelTesting the CRC Model

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

2. Inspect the description of each CRC index card to determine if a2. Inspect the description of each CRC index card to determine if adelegated responsibility is part of the collaboratordelegated responsibility is part of the collaborator’’s definition.s definition.

3. Invert the connection to ensure that each collaborator that is3. Invert the connection to ensure that each collaborator that isasked 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, determine4. Using the inverted connections examined in step 3, determinewhether other classes might be required or whetherwhether other classes might be required or whetherresponsibilities are properly grouped among the classes.responsibilities are properly grouped among the classes.

5. Determine whether widely requested responsibilities might be5. Determine whether widely requested responsibilities might becombined into a single responsibility.combined into a single responsibility.

6. Steps 1 to 5 are applied6. Steps 1 to 5 are applied iteratively iteratively to each class and through to each class and througheach evolution of the OOA model.each evolution of the OOA model.


OOT StrategyOOT Strategy

class testing is the equivalent of unit testingclass 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 applieintegration appliess three different strategies three different strategies thread-based testingthread-based testing——integrates the set of classesintegrates the set of classes

required to respond to one input or eventrequired to respond to one input or event use-based testinguse-based testing——integrates the set of classes requiredintegrates 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 tointegrates the set of classes required to

demonstrate one collaborationdemonstrate one collaboration


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

softwaresoftware Smoke testing steps:Smoke testing steps:

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

A build includes all data files, libraries, reusable modules, andA build includes all data files, libraries, reusable modules, andengineered components that are required to implement one or moreengineered components that are required to implement one or moreproduct functions.product functions.

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

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

The build is integrated with other builds and the entire product (inThe build is integrated with other builds and the entire product (inits current form) is smoke tested daily.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 recovery isforces the software to fail in a variety of ways and verifies that recovery is

properly performedproperly performed

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

from improper penetrationfrom improper penetration

Stress testingStress testing executes a system in a manner that demands resources in abnormal quantity, executes a system in a manner that demands resources in abnormal quantity,

frequency, or volumefrequency, or volume

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

systemsystem


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 annoyingannoyingdisturbingdisturbing

seriousseriousextremeextreme

catastrophiccatastrophic

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 ThoughtsDebugging: Final Thoughts

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.

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Chapter 13 Software Testing Strategies - Aalborg...

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