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Software Testing Essentials 1 www.qsitglobal.com

Testing Essentials Unit 1

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Software Testing Essentials 2www.qsitglobal.com

Topic Coverage

� Overview

� Definition and Principles of System Development

� Various phases of the systems development lifecycle (SDLC)

� Cross life cycle activities that overlap SDLC

� Different Models of SDLC

– Basic Models

– Extended Models




System Development Process

This process is called the System Development

Life Cycle (SDLC) because every system is

‘born’ and eventually ‘dies’.

�A system development process is a set of activities, methods, best

practices, deliverables and automated tools that stakeholders use to

develop and maintain information systems and software.


Why Design Systems?

� Information is a valuable resource that needs to be managed and not wasted.

�Systems are complex

easy to miss key details – Requirement Gathering

�Ad Hoc methods frequently fail to meet requirements.

Methodology

�Need to improve chance of developing a successful system.

Standards

�Any model of a solution is better than no model.

Previous data (Best practice)

�Companies do change, so systems change. –

Enhancement




Why Design System


Principles of Systems Development

� Get the Owners and Users Involved.

� Use a Problem-Solving Approach.

� Establish Phases and Activities.

� Establish standards for consistent

development and documentation.

� Justify systems as capital investments.

� Cancel project or revise scope if necessary.

� Divide and conquer.

� Design systems for growth and change.




Software Development Life Cycle

The period of time that starts when a software product is conceived and ends when the product is no longer available for use.

Consists of many phases (usually 5-8).

Phase is a related set of software engineering activities producing a work-product which may act as input for next phase.

Each phase provides an opportunity to understand the progress in the project.


Software Development – Major Activities

� Three additional Activities

– Scope/Project Definition

– Project planning (early)

– Support (after implementation)

Three major PhasesAnalysis: understanding business needsDesign: conceptualizing computer-system solutionImplementation: construction, testing, and installation




Scope/Project Definition PhaseServes as a bridge between Marketing Team and the Delivery Team

�To communicate the business acquisition with inputs

�To bring in organizational commitment for the project

�Identifying the core business need

�Setting and managing Project expectations

�To develop and link project objectives in measurable and quantifiable deliverables

�To obtain Management approval for the Project


Scope/Project Definition Phase

� To assess the readiness of the teams to carry out the Project

� To analyze the feasibility of the Project related work as well as

technology.

� To form the Peer Team for the Project.

� To provide adequate inputs to begin the Project

planning and execution Process.




Planning Phase

� Confirm project feasibility

� Produce project schedule

� Staff the project

� Launch the project


Analysis Phase

� Gather information

� Define system requirements

� Build prototypes for discovery of requirements

� Prioritize requirements

� Generate and evaluate alternatives

� Review recommendations with management




Design Phase

� Design and integrate the network

� Design the application architecture

� Design the user interfaces

� Design the system interfaces

� Design and integrate the database

� Prototype for design details

� Design and integrate the system controls


Implementation Phase

� Construct software components

� Verify and test

� Convert data

� Train users and document the system

� Install the system




Support Phase

� Maintain the system

� Enhance the system

� Support the users


Cross Life Cycle Activities

� Cross life cycle activities are activities that overlap many or all phases of the methodology

– Fact-finding

– Documentation and presentation

– Feasibility analysis

– Process and project management




Ensuring Quality Deliverables from SDLC

� Process Quality Assurance

– Process Audits: ISO

– Process Appraisals: CMMI

� Product Quality Assurance

– Testing

– Product Audits

• Configuration Management Audit

– Static Reviews

• Formal Technical Reviews- FTRs

• In-Formal Technical Reviews- InFTRs

• Inspection

� Defect Prevention & Management


Models of SDLC

A framework that describes the activities performed at each stage of a software development project.

� Basic Models:– Waterfall Model – Spiral model– V Model

� Extended Models– W Model– Extreme Programming– Rational Unified Process (UML)




Waterfall Model

� One of the first models of Software

development

� Each phase or activities are found in

nearly all models proposed since


Waterfall Strengths

� Easy to understand, easy to use

� Provides structure to inexperienced staff

� Milestones are well understood

� Sets requirements stability

� Good for management control (plan, staff, track)

� Works well when quality is more important than cost or schedule




Waterfall Deficiencies

� All requirements must be known upfront

� Deliverables created for each phase are considered frozen –

inhibits flexibility

� Can give a false impression of progress

� Little opportunity for customer to preview the system (until

it may be too late)


When to use the Waterfall Model

� Requirements are very well known

� Product definition is stable

� Technology is understood

� New version of an existing product

� Porting an existing product to a new platform.




V Model

� A variant of the Waterfall that

emphasizes the verification and

validation of the product.

� Testing of the product is planned in

parallel with a corresponding phase of

development


V-Shaped Strengths

� Emphasize planning for verification and validation of the

product in early stages of product development

� Each deliverable must be testable

� Project management can track progress by milestones

� Easy to use




V-Shaped Weaknesses

The disadvantage of the model is the coarse division into constructive work (including the implementation) on the left-hand side of the “V” and the more destructive tasks on the right-hand side.

– Here also the impression may develop that, after the implementation phase, a ready product can be delivered. A planned-in removal of defects and regression test is not given.


When to use the V-Shaped Model

� Excellent choice for systems requiring high reliability – hospital

patient control applications

� All requirements are known up-front

� When it can be modified to handle changing requirements

beyond analysis phase

� Solution and technology are known




Structured Evolutionary Prototyping Model

� Developers build a prototype

during the requirements phase

� Prototype is evaluated by end

users

� Users give corrective feedback

� Developers further refine the

prototype

� When the user is satisfied, the

prototype code is brought up to the

standards needed for a final

product.


Structured Evolutionary Prototyping Strengths

� Customers can “see” the system requirements as they are

being gathered

� Developers learn from customers

� A more accurate end product

� Unexpected requirements accommodated

� Allows for flexible design and development

� Steady, visible signs of progress produced

� Interaction with the prototype stimulates awareness of

additional needed functionality




Structured Evolutionary Prototyping Weaknesses

� Tendency to abandon structured program development for

“code-and-fix” development

� Bad reputation for “quick-and-dirty” methods

� Overall maintainability may be overlooked

� The customer may want the prototype delivered.

� Process may continue forever (scope creep)


Spiral Model

� Advantages:

– Tests covered Risk Analysis, Validation of Requirements and development

– Test phase is divided in to Module, Integration and Acceptance.

� Disadvantages:

– Testing follows Coding.

– Test Plan should be constructed after Design Phase.

– No defined activities associated with the removal of defects.

In the spiral-model a cyclical and prototyping view of Software development was shown.




Spiral Model Representation

Modified Waterfall Model � Spiral Model

Anal

yze

Des

ign

Dev

elo

p

Imp

lem

ent


Summary

� From the view of testing, all of the models presented previously are deficient in various ways:

– The test activities first start after the implementation

– The connection between the various test stages and the basis for the test is not clear

– The tight link between test, debug and change tasks during the test phase is not clear

� Extended Models help to remove the above mentioned disadvantages




Extended Model – W Model

Right hand side of the W contains not only the “destructive” test activities as in the V model but also the “constructive” change activities that are carried out as a result of the discovery of faults and defects.


Agile Testing

No Requirement

Specification required

Initially defined Testcases are used asRequirements.

These are then used afterthe implementation tohelp check the (sub-)product.




Extended Model – Rational Unified Process

� Inception phase:

Are defined the objectives, initial requirements and scope of the project.

� Elaboration phase:

The requisites are refined and completed. The architect design software solutions to the requisites (functional solution)

� Construction phase:

Software solution is constructed by developers.

� Transition phase:

The components are deployed and users are trained


The RUP Disciplines are:

� Business Modeling: Maps the company business which relates to the project. More used in large or complex projects.

� Requirements: Collect requisites of the key users.

� Analysis & Design: Design the software requisites in UML models

� Implementation: Implements the software solution in software components and database components

� Test: Test the constructed components

� Deployment: Install components and train users in your use

� Configuration & Change Management: Maintain and manage the artifacts produced by the software team

� Project Management: Manage, plan and distribute activities of the team, focusing in quality, schedule, budget and risk attack.

� Environment: Maintain tools configuration and environment aspects in order to the development team.

Extended Model – Rational Unified Process




End of Chapter

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Software Testing Essentials 38 www.qsitglobal.com

Testing Essentials Unit 2

QSIT- Quality Solutions for Information Technology Pvt. Ltd.,

A 806 & 807, Mittal Tower,

BANGALORE- 560 001,INDIA

URL: www.qsitglobal.com

PH: +91 80 41134334

Fax: +91 80 25597445




Topic Coverage

� Quality Perspective

� Software testing

� Objectives of software testing

� Role of software testing

� Benefits from software testing

� Preventive and corrective actions


Software Product

Software

Product

Documentatio

n

Data

Procedures

Deliverable to

customer and

end user

Fit for

Environment

Data

Structur

e

People

Rules Standards

Risk: A factor that could result in

Future negative consequences;

Express as impact and likelihood

Computer

Program




Causes of Software Defect

� Error (mistake) A human action that produces an incorrect result

� Defect (bug, fault) A flaw in a component or system that can cause the component or system to fail to perform its required function

� Failure Deviation of the component or system from its expected delivery service or result


How does defects affect?

� Errors in the specification, design and implementation of the software and system

� Errors in use of the system

� Environmental conditions

� Intentional damage

� Potential consequences of earlier errors, intentional damage, defects and failures




Fundamental of Software Testing QC and QA

� Quality Control: The processes and methods used to monitor work and observe whether requirements are met.

� Quality Assurance: A planned and systematic pattern of actions necessary to provide adequate confidence that the product optimally fulfills customers' expectations.


Corrective and Preventive Measures

AddressingDefects

Appraisal Quality

Preventive Quality

Process Improvement

Testing Training

Process

Maturity

Metric

Program

Audits &

Assessments

Inspection

Walkthroughs

Reviews

•Data Gathering & Analysis

•Fault Analysis

•Root Cause Analysis




Preventive Quality

Training refers to the acquisition of knowledge, skills, competencies as a result of the teaching of practical skills and knowledge that relate to specific useful Competencies

Metric programMetrics derive information from raw data with a view to help in Decision making. A measurement scale and the method used for measurement. [ISO 14598]

Audits and AssessmentsAn inspection/assessment activity that verifies compliance with plans, policies and procedures


Preventive Quality (con td…)

ReviewAn evaluation of a product or project status to ascertain discrepancies from

Planned results and to recommend improvements. Examples include

management review, informal review, technical review, inspection, and

walkthrough. [After IEEE 1028]

Walk ThroughA step-by-step presentation by the author of a document in order to

gather information and to establish a common understanding of its

content. [Freedman and Weinberg, IEEE 1028]

InspectionA type of review that relies on visual examination of documents to

detect defects, E.g. violations of development standards and non-

conformance to higher level documentation. The most formal review

technique and therefore always based on a documented procedure.

[After IEEE 610, IEEE 1028]




Software Testing- Definitions

� Definition (1)

– Process of exercising or evaluating a system or system component by manual or automated means to verify that it satisfies specified requirement(IEEE 83a)

� Definition (2)

– Structured process that uncovers the defects in a software product.

– Destructive in nature (dismantling the wishful assumption that code is bug-free)

� Definition (3)

– Testing is a process of executing a program with the intent of finding errors(Myers)


Testing Glossary

� Manual Testing

– Refers to a corrective process to meet customer requirements without

using any automation tool.

� Automated testing

– It is the process of automating the manual testing activities




Testing Glossary

Static testing:

Testing of a component or system at specification or implementation level

without execution of that software, e.g. reviews or static code analysis.

Dynamic testing:

Testing that involves the execution of the software of a component or

system.


Testing Glossary

Functional testing:

Testing based on an analysis of the specification of the functionality of a

component or system.

Non-functional testing:

Testing the attributes of a component or system that do not relate to

functionality, e.g. reliability, efficiency, usability, maintainability and

portability.




Software Testing- What Does it Ensure?

� Find defects in product

� Demonstrate difference between specifications and developed system

� Ensure product works with negligible risks.

� Establish confidence in the product

� Offer advise on product quality and risks

� Insight to improving testing process


Limitations of Software Testing

� Does not generalize system behavior

� Does not guarantee bug free product

� No substitute for good programming




Role of Software Testing

� Primary Role

– Verification - The process of determining whether or not the products of a given phase in the lifecycle fulfill a set of established requirements

� Are we doing things right? (Process)

� Are we building the system right?



– Validation - The process of evaluating a system or component, during or at the end of the development life cycle, to determine whether it satisfies specified requirements.

� Are we doing the right things? (Requirements)

� Did we build the right system?





� Secondary Role

– Build Confidence to “Ship the Product”

– Insight into Software Process

– Improve the Software Testing Process


Some Facts…About Testing...

� No substitute for good programming

� It can't prevent bugs

� Can only identify them

� However...

When testing is used in combination with good programming, you can deliver software that is of high quality, reliability and has a very low defect rate.




Aspects that hinder effective software testing

� Belief that the system works

� Negative attitude towards effective testing

� Conflict between testers and developers

� Testing is expensive

� Delivery commitments


Principles of Software Testing

Early TestingTesting activities should start as early as possible in the software orsystem development life cycle and should be focused on definedobjectives

Defect ClusteringA small number of modules contain most of the defects discoveredduring pre-release testing or show the most operational failures

Avoid Pesticide paradoxIf the same tests are repeated over and over again, eventually thesame set of test cases will no longer find any new bugs. To overcomethis, the test cases need to be regularly reviewed and revised, andnew and different tests need to be written to

Testing Shows Presence of Defects

Testing can show that defects are present, but cannot prove thatthere are no defects. Testing reduces the probability of undiscovereddefects remaining in the software but even if no defects are found, itis not a proof of correctness




Principles of Software Testing

Testing is context dependent

Testing is done differently in different contexts. Ex: Testing a retailweb site is different from testing a embedded application for anAerospace application

Absence of Errors fallacy

Finding and fixing defects does not help if the system built isunusable and does not fulfill the users’ needs and expectation

Exhaustive Testing is Impossible

Testing everything (all combinations of inputs and preconditions) isnot feasible except for trivial cases. Instead of exhaustive testing,we use risk and priorities to focus testing efforts

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