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Chapter Chapter 77

Software Testing Software Testing StrategiesStrategies

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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.

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What Testing ShowsWhat Testing Shows

errorserrors

requirements conformancerequirements conformance

performanceperformance

an indicationan indicationof qualityof quality

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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

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Testing StrategyTesting Strategy

unit testunit test integrationintegrationtesttest

validationvalidationtesttest

systemsystemtesttest

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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

For OO softwareFor 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 individual module (the conventional view) to an OO class that encompasses attributes and operations and class that encompasses attributes and operations and implies communication and collaborationimplies communication and collaboration

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Strategic IssuesStrategic Issues

State testing objectives explicitly. State testing objectives explicitly. Understand the users of the software and develop a profile for each user Understand the users of the software and develop a profile for each user

category.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 itselfBuild “robust” 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 Conduct formal technical reviews to assess the test strategy and test

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

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Unit TestingUnit Testing

modulemoduleto beto betestedtested

test casestest cases

resultsresults

softwaresoftwareengineerengineer

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Unit TestingUnit Testing

interface interface local data structureslocal data structures

boundary conditionsboundary conditionsindependent pathsindependent pathserror handling pathserror handling paths

modulemoduleto beto betestedtested

test casestest cases

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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

test casestest cases

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Integration Testing StrategiesIntegration Testing StrategiesOptions:Options:

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

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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

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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

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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

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Object-Oriented Object-Oriented TestingTesting

begins by evaluating the correctness and begins by evaluating the correctness and consistency of the OOA and OOD modelsconsistency of the 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 integration focuses on classes and their execution integration focuses on classes and their execution

across a ‘thread’ or in the context of a usage scenarioacross a ‘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, test case design draws on conventional methods, but also encompasses special featuresbut also encompasses special features

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Broadening the View of Broadening the View of “Testing”“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 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).

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Testing the CRC ModelTesting the CRC Model

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

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

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

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

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

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

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OOT OOT StrategyStrategy

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 applied three different strategiesintegration applied three different strategies thread-based testing—integrates the set of classes thread-based testing—integrates the set of classes

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

required to respond to one use caserequired to respond to one use case cluster testing—integrates the set of classes cluster testing—integrates the set of classes

required to demonstrate one collaborationrequired to demonstrate one collaboration

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

product softwareproduct software 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.

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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

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Debugging: Debugging: A Diagnostic ProcessA Diagnostic Process

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The Debugging ProcessThe Debugging Processtest casestest cases

resultsresults

DebuggingDebugging

suspectedsuspectedcausescauses

identifiedidentifiedcausescauses

correctionscorrections

regressionregressionteststests

new testnew testcasescases

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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

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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

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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.

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Debugging TechniquesDebugging Techniques

brute force / testingbrute force / testing

backtrackingbacktracking

inductioninduction

deductiondeduction

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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.

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