SOFTWARE CONSTRUCTION SOFTWARE CONSTRUCTION

AND TESTINGAND TESTING

Software Construction & TestingSoftware Construction & Testing

What is software construction? What is software testing? How important are construction & testing? What are some of the “critical success

factors” for construction & testing? Who should be involved in the

construction & testing activities?

Software Construction & TestingSoftware Construction & Testing

Labor intensive activityLabor intensive activity

Tools are requiredTools are required

Blueprints are essentialBlueprints are essential

Mistakes can be deadlyMistakes can be deadly

Weariness and Stress are commonWeariness and Stress are common

Software Construction & Testing - A Large ProjectSoftware Construction & Testing - A Large Projectfrom LORAL (formerly IBM Federal Systems Div) *from LORAL (formerly IBM Federal Systems Div) *

Flight Software in Space ShuttleFlight Software in Space Shuttle 500 KLOC 500 KLOC Software Production Facility SimulatorSoftware Production Facility Simulator 1,700 KLOC1,700 KLOC Mission & Payload Control CentersMission & Payload Control Centers 4,000 KLOC4,000 KLOC Launch Processing SystemLaunch Processing System 2,500 KLOC2,500 KLOC Space Lab (prototype version)Space Lab (prototype version) 800 KLOC 800 KLOC

Total:Total: 9,500 KLOC9,500 KLOC New Version every 4-8 monthsNew Version every 4-8 months 10-53 KLOC changes each time10-53 KLOC changes each time

* circa 1994

* Caldwell, Bruce, “Taming the Beast”, InformationWeek, 3/10/97, pp 38-48.

Software Construction & Testing -Software Construction & Testing -A Large Project from Inland Steel Industries, Inc. *A Large Project from Inland Steel Industries, Inc. *

$4.6B Revenue (#6) $74.4M I.S. Budget 466 I.S. Employees Order Fulfillment Sys 27 Integrated Applics. 18 Reeng bus. process Almost 4 years:

1993 - Feas & Analysis ‘94-’96 Dev, Imple. in 3

phases

400 Person-years with 200 technologists

Replaced 30-year old sys 65,000 Function Points 7 Million LOC Cost: $37M; Save: $25M

(one-time); $9M Annually Developed On-Time and

Within Budget - aka “A Miracle”

Software Construction & Testing Software Construction & Testing - Software Design Principles- Software Design Principles

Software should work correctlySoftware should work correctly

Software must conform to requirements specificationSoftware must conform to requirements specification

Software must be reliable over time and dataSoftware must be reliable over time and data

Software must be evolutionarySoftware must be evolutionary

Software must be easy to useSoftware must be easy to use

Software should be easy to test & implementSoftware should be easy to test & implement

Software should use computer resources efficientlySoftware should use computer resources efficiently

Verification and Validation*Verification and Validation* Verification: The process of evaluating a system or

component to determine whether the products of a given phase satisfy the conditions imposed at the start of that phase. (Mainly a paper-based activity that requires you to confirm that each stage of the development conforms to the requirements defined in the previous stage.)

Validation: The process of evaluating a system or component during or at the end of the development process to determine whether it satisfies specified requirements. (Mainly a confirmation that the implemented system/component actually works to specification.)

* IEEE Standard Glossary of Software Engineering Terminology, 1994

Hierarchical View of Software Construction

Statement(sequence, selection, iteration)

EXAMPLES

X = X + 1MOVE ACCT TO NEWACCTIF X = 25...DO WHILE ...

(one or more statementscombine to form a module)

Module(paragraph, procedure, subroutine)

COMPUTE-NET-PAYSALESTAX(AMT,TOTAL)

Program

(one or more modulescombine to form a program)

INVOICE PROGRAMORDER ENTRY PROGRAMELEVATOR PROGRAM

Sub-System or System

(one or more programs combineto form a sub-system or system)

HP

PDS

(software, hardware, people,procedures, data)

Hierarchical View ofObject-Oriented SoftwareConstructionStatement

(sequence, selection, iteration)

(one or more statementscombine to form a service)

Service

(one or more services belongto a Class or Class-with-Objects)

Sub-System or System

(one or more Class-with-Objects combineto form a sub-system or system)

HP

PDS

(software, hardware, people,procedures, data)

Class with Objects

Attributes

Services

Software Construction StrategiesSoftware Construction Strategies

TOP-DOWNTOP-DOWN

BOTTOM-UPBOTTOM-UP

MIDDLE-OUTMIDDLE-OUT

High-level to low-High-level to low-level; user interface level; user interface to detail logicto detail logic

Reverse of the aboveReverse of the above

Some of bothSome of both

These strategies are discussed in more detail in the Testing Section

Cohesion Coupling

Two Software Evaluation MetricsTwo Software Evaluation Metrics

COHESION: COHESION: The measure of strength The measure of strength

of the of the

interrelatedness of statements within interrelatedness of statements within

a modulea module

High (best)

Low (worst)

• Functional

• Informational

• Communicational

• Procedural

• Temporal

• Logical

• Coincidental

Cohesion*Cohesion*

* adapted from: Software Engineering, Pressman, R. S., McGraw Hill, 1987

“Scatter-brained” module “Single-minded” module

low (“worst”) high (“best”)

Coincidental Logical Temporal ..... Informational Functional

COHESION: COHESION: The measure of strength The measure of strength

of the of the

interrelatedness of statements within interrelatedness of statements within

a modulea module

High (best)

Low (worst)

• Functional - one action or goal

• Informational - multiple independent actions on

the same data

• Communicational - series of steps on same data

• Procedural - series of steps for an action

• Temporal - series of related actions related in time

• Logical - series of related actions

• Coincidental - multiple, unrelated actions

Cohesion - examples - 1 of 3Cohesion - examples - 1 of 3

• Coincidental cohesion module

Logic to produce Payroll reportLogic to produce Production reportLogic to produce Sales reportLogic to check e-mailetc...

Onemodule

Cohesion - examples - 2 of 3Cohesion - examples - 2 of 3

• With (x) = Coincidental cohesion• Without (x) = Logical cohesion

Display date & time on screenPrompt user for student id numberLook up student id number in STUDENT tableIF found: Prompt user for password Validate password Process course seat registration request Check to see if user has email waiting (x) Check to see if user’s health record is up-to-date (x)ELSE IF not found: do error processingEND

Cohesion - examples - 3 of 3Cohesion - examples - 3 of 3

• Functionally cohesive modules

Logic to display date

Logic to display time

Logic to prompt user for student id

Logic to validate student id

Logic to handle error condition

Logic to prompt user for password

Logic to ..... etc.

Each of theseis a separatemodule

COUPLING: COUPLING: The measure of strengthThe measure of strengthof the connection between modulesof the connection between modules

High (worst)

Low (best)

• Content

• Common

• Control

• Stamp

• Data

• No Coupling

Coupling*Coupling*

* adapted from: Software Engineering, Pressman, R. S., McGraw Hill, 1987

“highly independent” module “highly dependent” module

low (“best”) high (“worst”)

No coupling Data Stamp Control Common Content

COUPLING: COUPLING: The measure of strengthThe measure of strength

of the connection between modulesof the connection between modules

High (worst)

Low (best)

• Content - direct branch into middle of module

• Common - global reference of variables

• Control - control element being passed

• Stamp - pass an entire data structure

• Data - variables or fields only being passed

• No Coupling

Software Testing PrinciplesSoftware Testing Principles User-accepted test planUser-accepted test plan General testing strategy/philosophy:General testing strategy/philosophy:

Cause and discover errors Rules of reasonableness should prevail

Testing Strategies:Testing Strategies: Top-DownTop-Down Bottom-UpBottom-Up Middle-outMiddle-out HybridHybrid Black boxBlack box White boxWhite box AlphaAlpha BetaBeta

Software Testing Methodology Showing

Feedback/Fallback LoopUser Acceptance Testing

System Testing

Function Testing

Integration Testing

Unit Testing

Module A

Stub B Stub C Stub D

Module A

Module B Stub C Stub D

Stub E Stub F

Module A

Module B Stub C Stub D

Module E Stub F

Stub Testing (shaded module is the current one being tested)

Module A

Stub B Stub C Stub D

Module A

Do Stub BDo Stub CDo Stub D

End Module A

Stub B

Display “now in Stub B”Return

Stub C

Display “now in Stub C”Return

Stub D

Display “now in Stub D”Return

Calling Stub Modules During Construction & Testing

SystemsAnalysis

SystemsDesign

SoftwareDesign

ProgramDesign

ModuleDesign

UserSpecification

SystemSpecification

SoftwareSpecification

ProgramSpecification

ModuleSpecification

AcceptanceTesting

SystemTesting

FunctionTesting

IntegrationTesting

UnitTesting

Programming

Framework for Information Systems Testing

Validation and Verification Define the “Problem”

Solve the “Problem”

Prove it

Validation - process done by s/w

developer

Verification - process done by customer

1 of 2

Validation and Verification

2 of 2

Need(s)

Design and Implement

Component Test

Sub-system TestSub-system Requirements

System Requirements

Component Requirements

System Test

DeliveredSystem

That’s all folks!That’s all folks!