SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Analysing and testing source code - slide 1 Software engineering for real-time systems

SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Analysing and testing source code - slide 1

Software engineering for real-time systems

Section 11

Analysing and testing source code


Objectives

To:Explain the underlying concepts of the testing of source code.

Describe the basics of static and dynamic analysis.

Introduce code complexity metrics.

Describe coverage analysis and its use as part of the dynamic analysis process.

Illustrate test issues specifically related to object-oriented programming constructs.

Introduction


Introduction to software testing

Part 1

Overview


WHY TEST SOFTWARE?

The really important questions:

Will it work properly?

Will it be reliable?

Will it to be easy to build?

Is it a quality design?

Will it be easy to maintain?

Why test software?


Analys isof source code quality

T estof source code behaviour

Evaluation ofsource code

Language-

quality andstandards

Coding-

quality andstandards

Functionalcorrectness

Tem poralcorrectness

Unexpectedbehaviour

and programviolations

Preventing errors

Detecting errors

Approaches to code testing


Error detection

Software source codetesting

Error prevention

Code INSPECTION(static analysis)

Code EXECUTION(dynamic analysis)

Software code test techniques


Software testing steps

Software system

Software sub-system 1 Software sub-system 2

Majorsoftware

function 1

Majorsoftwarefunction 2

Majorsoftwarefunction 3

Code unit1

Code unit3

Code unit2

Code unit5

Code unit4

Integration of parts

Test units

Integrate units then test functions

Integrate functions then test sub-systems

Integrate sub-systems then test the complete system


Introduction to static analysis

Part 2

Static Analysis


Source code analys is(static analys is)

Manual staticanalysis

Autom ated staticanalysis

Analysis ofattributes

Analysis offunctionality and

correctness

Static analysis techniques


Automatic staticanalysers

Program attributeanalyser

Program verificationanalyser

Programstructure

(control flowanalysis)

Data usage(dataflowanalysis)

Informationflow

(informationflow analysis)

Program functionalrelationships

(semantic analysis)

Programcorrectness(compliance

analysis)

Automated static analysis tools


Evaluating program structure - cyclomatic complexity measures

Controlflow

graphGraph complexity measured using

Cyclomaticcomplexitytechniques

Output from module

Source codedecision logic

Input to module

Structure described using a

McCabe’s cyclomatic complexity metric: a measure of the amount of decision logic in a code unit

Cyclomatic complexity value: the number of independent paths through a control flow graph


Control flow graph - simple sequence structure

Cyclomatic complexity value v(G): the number of independent paths through a control flow graph.

Here v(G) = 1

{

Accel [0] = Xnew; Accel [1] = Xold; Accel [2] = Ynew;

}

Statement 1

Statement 2

Statement 3

Node 1

Node 2

Node 3

Edge(1-2)

Edge(2-3)

Code of 'module'Corresponding flow

graph

Statement 1

Statement 2

Statement 3

Flowchart


Control flow graph - simple selection structure

{

if (P ressure > H ighPressureA larm ) cout << "\nH igh pressure alarm "; else cout << "\nPressure OK";

cout << "\nEnd of pressure test";

}

Construct 1

Construct 2

Construct 3

Construct 4

Node 2

Node 1

Edge (1-2)

Edge (1-3)

Edge (3-4)

Edge (2-4)

Node 3

Node 4

Code of 'm odule'

Corresponding flow graph

Statement

Flowchart

Statement

Statement

?

v(G) = 2


Control flow graph - simple iteration structure

{

while (DataValue < 10) { cout << "\nInput data value"; cin >> DataValue' cout << DataValue; } /* end while */

cout << "\nEnd of test";

}

Construct 1

Construct 2

Construct 3

Construct 4

Code of 'module'

Construct 5

Node 1

Edge(1-2)

Edge(2-3)

Edge(3-4)

Edge(4-1)

Node 5

Corresponding flow graph

Node 3

Node 2

Node 4

Edge(1-5)

Statement

Flowchart

Statement

?

Statement

Statement

v(G) = 2


Control flow graph -highly complex

structure

Control flow graph -simplest structure

achievable

Example control flow graphs


Introduction to dynamic analysis

Part 3

Dynamic Analysis


Black box and white box testing

Two ways of testing code

Overall function Internal workings

‘Black box’ testing

Performed at the interfaces

‘White box’ testing

Performed on the implementation


Inputstim ulus

Measuredresponses

Softwareundertest

(a) Fundam ental concept of dynam ic testing

Softwarespecification

Testcases Measured

responses

Com parisonand results

analysis

Calculatedresponses

Test scriptSoftware code for

testing

Codeexecution

(b) Detailed aspects of dynam ic testing

Basis of dynamic testing


Coverage analyzer

Creation oftest data

Control oftest data

supply

Control ofsoftware

execution

Recording ofsoftware

responses

Analysis of tests

Generation ofpredicted

results

Com parison of actualand predicted values

Error reporting

Data generator

Test driver

Prediction generator

Fault diagnostic ian

Results analyzer

The test harness


Dynam ic testing tool features

Test scriptgeneration

Softwareexecution

Softwareperform ance

(tim ing)

Datacorrectness

checking

Em ulation andsim ulation of

target system s

Features of general-purpose dynamic testing tools


Individual white box tests for coverage analysis Name

Exercise each statement of a program at least once. Statement testing

Exercise each branch in a program at least once Decision or branchtesting

Exercise all possible paths through the program. Path testing

Exercise all logical conditions within a program. Condition testing

Coverage analysis and white box testing

Coverage analysis

‘A measure of the effectiveness and completeness of code testing.’



Define testobjectives and

write test cases

W rite sourcecode

Test casedefinition file

Test scriptcode file

Com pilecode

Com pilecode

Linkcode

Source codefile

Generate testscript code

Executablecode file

Build the test un it

Test the software(execute the code)

Results file

Tool library(linkable file)

Basis of a practical dynamic testing tool



Define the testobjectives and write

the test cases

W rite thesource code

Test casedefinition file

Test scriptcode file

Com pilethe code

Com pilethe code

Link allcode

Source codefile

Generate the testscript code

Executablecode file

Build the test un it

Test the software(execute the code)

Results file

Tool library(linkable file)

Instrum entedsource code

file

Instrum ent thesource code

Static analysislist file

Analysisdirectives

file

Dynamic testing and coverage analysis tool


Integration and testing

Part 4

Integration and

test strategies


Combined unit and integration testing

Unit A

Unit A2Unit A1

Test code for unitA

Test 2

Integrate units A1 and A2 to form A

Test code for unitA1

Unit A1

Test 1(a)

Test code for unitA2

Unit A2

Test 1(b)

Phase 1: test individual units.

Phase 2: test the combined unit.

This test must exercise all features of A1 and A2.


Reduced integration testing

v

v

Call node

(a) Original graph - v(G) = 6

Call node

(a) Reducedl graph - v(G) = 2

Full flow graph of the integrated unit A.

Reduction steps:

1. Identify ALL control structures of units A1 and A2 not concerned with external units (A).

2. Remove these from the flow graph.

Reduced flow graph of the

integrated unit


Class and object testing

Part 5

OO systems -



Structure

Function Dynamics

AttributesOperations

OBJECT FEATURES

Structure

Function Dynamics

ObjectsObjectrelationships

SYSTEM FEATURES

Controller

Sensor

Actuator



Weighed methods per class (WMC).

Depth of inheritance tree (DIT).

Number of children (NOC).

Coupling between objects (CBO).

Response for a class (RFC).

Lack of cohesion for methods (LCOM).

OO metrics in general use


Use of OO metrics

Evaluation ofcompleteness andself-containment

Assessment ofdesign complexity

Prediction of requiredtest effort

Use of OO metrics(class and object)

Estimation ofcoding errors

Ÿ LOCŸ ADŸ MD

Ÿ MHFŸ AHFŸ LCOM

Ÿ DITŸ NOCŸ LCOMŸ WMC

Ÿ WMCŸ RFCŸ MHFŸ CBO


SensorClass

ShowData

C lasses and m ethods

ShowData

R esponse to the ca ll on the c lass m ethod (s)

SensorClass

ShowData

AttitudeClass

AttitudeData

HeightC lass

HeightData

SpeedClass

SpeedData

ShowData ShowData ShowData

ShowData ::A ttitudeClass

ShowData ::HeightC lass

ShowData ::SpeedClass

(a) Im plic it flow of control with polym orphic operations

(a) F low of control without inheritance

Inheritance, polymorphism and testing issues


Client object A

Client object C

Client object B

ShowData :SpeedClass

ShowData :HeightC lass

ShowData :A ttitudeClass

Multiple clients using multiple servers having polymorphic methods

THE question: How much testing is needed?


Client object A

Client object C

Client object B




Client object A

Client object C

Client object B




Client object A

Client object C

Client object B




(a) Full and com prehensive test strategy

(b) M inim um acceptable test stragegy

(c) Com prom ise test stragegy

Alternative test strategies with multiple clients/servers


You should now:

Be able to explain the underlying concepts of software testing of source code structures.

Know what static and dynamic analysis are and how they may be carried out. Appreciate the features and use of the McCabe cyclomatic complexity metric. Know what white box and black box testing entails. Recognize that dynamic analysis includes both testing and coverage analysis. Know what test strategies can be applied to integration testing. Realize that OO designs bring new problems into the software test arena.

END OF SECTION ‘Analysing and testing source code’

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SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Analysing and testing source code - slide 1 Software engineering for real-time systems