1 software testing and quality assurance lecture 2 software verification & validation
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1
Software Testing and Quality Assurance
Lecture 2
Software Verification & Validation
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Lecture Outline Static V &V techniques
Walkthroughs. Technical Reviews. Software Inspections.
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Walkthroughs Usually done in a single meeting. Evaluate a software product to
Find anomalies & improve the software product.
Consider alternative implementations. Evaluate the conformance to standards
and specification. Perform training of the project teams.
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Suitability forthe intended
use?
Technical Reviews
Software Product
•Review Report•Action Item List
Technically Qualified TeamEvaluates
Rework/Follow-up
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Software Inspection Formalized approach to document
reviews. Intended explicitly for defect detection
(not correction). Defects may be logical errors &
anomalies in the code. For example, An un-initialized variable Non-compliance with standards.
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Software Inspection Remove errors as near source as
possible; hence, reducing costs of rework.
It’s success depends on The inspection process, Checks applied; The diligence of the inspectors.
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Inspection pre-conditions Precise specification must be available. Team members must be familiar with
the organization standards.
Inspections will increase costs earlyin the software process.
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Software Inspections
Time
No. of Employees
PlanningRequirements
Design Coding
Testing
Without Inspection
With Inspection
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Inspection Process
Planning
Overview
IndividualPreparation
Rework
Follow-up
InspectionMeeting
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Inspection Steps Reader paraphrases design, describing how it
will be implemented. Questions raised during discourse, only
pursued until error recognized. Error noted (but not solution) and classified
by severity. Written report of inspection prepared.
Important to inspect modified products. Re-inspection to avoid ‘bad fix’ problems.
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Software Inspection Overview
Operation 1 I
Rework
Analysis
Fix short term problems
Error feedback
•Learning input for inspectors•What error types to look for
•Better ways to find error types
Feedback
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Feedback Inspection provide detailed real-time
feedback to developers Process control using inspection
Identification of error prone modules; and Distribution of error types
Inspections should lead to Process Improvement
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Feedback Inspection success depends on
Management attitude Conduct of trained moderator
Inspections should not be used for performance appraisals
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Software Inspection Overview
Operation 1 Operation 2I
Rework
Analysis
Fix short term problems
Error feedback
•Learning input for inspectors•What error types to look for
•Better ways to find error types
•Error prone modules ranked.•Error types distributions ranked
For Special Attentions
Feedback
Feed forward
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Rate of ProgressRate of progress (man/hours)
Process Operations Design Code objectives
Overview 500 - communication
preparation 100 125 education
inspection 130 150 Find errors
Rework 20 16 Remove errors
Follow-up - - Ensure resolutions of errors
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Error Analysis Finding errors is difficult
Condition people to seek high occurrence, high cost error types.
Take representative sample of code; Analyze errors
Type and origin of error; cause and salient indicative feature
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Stages of Static Analysis
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Control Flow Analysis Condition statements;
Is the condition correct? Loop statements;
Is each loop certain to terminate? Case statements;
Are all possible cases accounted for?
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Data Check Are all program variables initialized
before their values are used? Have all constants be used? Is there any possibility of buffer
overflow?
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Interface Analysis Do all function and method calls have
the correct number of parameters? Are the parameters in the right order?
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London Ambulance Service Case Study
ComputerAided
Dispatch
Server
Server
Automatic VehicleLocation System
RadioCommunicationInfrastructure
Ambulance
PRINCE Development Methodology was selected for the development
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London Ambulance Service Case Study Throughout the project there are references
to only functional testing No static V & V process.
The draft project plan as provided by the supplier left no time for review and revision.
As a result, …….. For example, Lack of formal clarification how the PRINCE
methodology was to be applied.
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Key Points Focus objectives of static V &V
techniques such as software inspection. Identify error types to get maximum
benefits out of static V & V techniques. Analyze inspection results and use it for
process improvement.
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