CS352 – Software Engineering IILecture 17: SW Quality Assurance Landscape

Slides byMohammad El-Ramly, PhD

حديثشريف

أحدكم 1. عمل إذا يحب الله إنيتقنه أن عمال

على 2. اإلحسان كتب الله إنشئ كل

Lecture 17 Outline

1.Understanding SW Quality Attributes2.Understand the value of SW QA3.Quality Landscape4.SW QA Jobs and Certificates5.Effectiveness of QA Techniques

Readings are essential for this course.Reading: (7) Code Complete Chapter 20

Accompanying site: http://cc2e.com/

What is SW Quality?

• Customer’s Perspective System does not crash System follows documentation & contract System is logical and easy to use

• Developer’s Perspective System is easy to change System is easy to understand System is pleasant to work on

External Quality Characteristic

● Correctness. The degree to which a system is free from faults

in its specification, design, and implementation.

● Usability. The ease with which users can learn and use a

system.

● Efficiency. Minimal use of system resources, including

memory and execution time.

External Quality Characteristic

● Reliability The ability of a system to perform its required

functions under stated conditions whenever required—having a long mean time between failures.

● Robustness The degree to which a system continues to

function in the presence of invalid inputs or stressful environmental conditions.

External Quality Characteristic

● Integrity The degree to which a system prevents

unauthorized or improper access to its programs and data.

Ensuring that data is accessed properly

● Adaptability The extent to which a system can be used,

without modification, in applications or environments other than those for which it was specifically designed.

Internal Quality Characteristic

● Maintainability The ease with which you can modify a

software system to change or add capabilities, improve performance, or correct defects.

● Flexibility The extent to which you can modify a system

for uses or environments other than those for which it was specifically designed.

Internal Quality Characteristic

● Reusability The extent to which and the ease with which

you can use parts of the system in other systems.

● Understandability / Readability The ease with which you can comprehend a

system at organizational and detailed levels.

Total Quality Management

• Factories• Goal is for every item coming off the

assembly line to be perfect • Management, production, engineering, QA• Everyone is involved in quality• Develop a reliable, repeatable process• Continuously improve the process

The Cost of Poor Quality

• Money• Time• Resources• Lives• Reputation• Business

Failure Costs

• Internal Rework Repair Failure analysis

• External Resolving complaints Returning and replacing product Help line

Prevention Costs

• Prevention Planning Managing and collecting information Reviews

• Appraisal Inspection Testing

The Cost of Poor Quality

Techniques for Improving SW Quality

1.What can we do improve quality ?

• SW QA is a wide spectrum of activities conducted through out the development process that focus on: Product quality Process quality

Techniques for Improving SW Quality (Code Complete)

1.SW Q Objectives & Planning2.Explicit QA Activities3.Testing Strategy4.SE Guidelines5.Formal / Informal Technical Reviews6.Change-control Procedures7.Measurement of Results8.Prototyping

Software Quality

Landscape

Plannin

g

Requir

emen

ts

Design

Develo

pment

Testin

g

Guidelines,

Standards and

Templates

QA Planning

and Budgeting

Testing

Debugging

Reviews

Refactorin

g

Requirements

V & V

Design R

eview

Collaborative

Development /

Reviews

Metrics

Change and Configuration Management

Bug Tracking Surveys

Deploym

ent &

Maintenanc

e

M a n a g e m e n t

Contract

Review

1. SW Quality Objectives

• Decide explicit quality characteristics1.Inform the developers2.They are more likely to achieve quality

objectives if they now them.3.Review their work

• Study by G M Weinberg, E L Schulman, Goals and Performance in Computer Programming (1974)

2. Explicit QA Activities

• QA should be perceived as a primary not secondary goal

• QA should be an organizational culture.• Organization should train developers that

quality is a priority.

3. Testing Strategy

• Develop a test strategy with product requirements, architecture and design.

• Or even consider test-driven development.

4. SE Guidelines

• Decide on guidelines, templates, checklists and standards to follow. Requirements, architecture and design

guidelines. Templates for plans, reports, etc. Coding style. File naming conventions.

• Apply them and enforce them in every phase.

5. Reviews

• Informal Reviews Desk-checking Walk through

• Formal Technical Reviews Act as a “quality gate” Catch problems at the “lowest-value” stage—that is, at

the stage in which problems cost the least to correct. Can be a peer review, a customer review, an,

inspection, or an external audit.

• Changing hurts quality. Remember the Vaza

• Uncontrolled changes: Requirements => unstable designs and code Design => Inconsistency with req. and code Code => Inconsistency / invalid doc.

• Adopt incremental development• Adopt Configuration and Change Management

6. Change-control Procedures

• Measuring what ? 3 P => Product, Project and Process Quality attributes.

• Measurements tells you if QA plan failed or succeeded.

• Can be the basis for improvement.

7. Measurement of Results

• Develop realistic model of the system’s key functionalities. UI to evaluate usability Key calculations to see their results, memory

requirements and performance

• Studies suggest that prototyping can lead to better designs, better satisfaction of user needs and improved maintainability.

8. Prototyping

CS42813-32

SQA Manager

• Responsible for SQA policy Develops testing plan Checks that plan is being followed Develops review process Trains reviewers Monitors reviews Develops customer survey plan …

• Nonin Medical, Inc. is a rapidly growing international medical device manufacturer that has been designing and distributing high quality medical monitoring devices since 1986.

• Responsible for ensuring software quality within complex medical device products through the development and execution of software test plans by way of verification procedures based upon software and system specifications

• http://www.nonin.com/JobPost.aspx?ID=243

SW QA Engineer Ad.

• Review product design documentation to ensure that requirements stated are correct, unambiguous, and verifiable.

• Consult with product development to evaluate system interfaces, operational requirements, and performance requirements of overall system.

• Define test methods and create test plans for new or updated software projects.

• Recommend design improvements or corrections to engineers throughout the development process.

• Maintain effective communication with the project software engineers..

SW QA Engineer: Duties & Responsibilities

• Execute test plans and create test reports to describe program evaluation, testing, and correction.

• Monitor program performance after implementation to prevent reoccurrence of program operating problems and ensure efficiency of operation.

• Conduct compatibility tests with vendor-provided programs.

SW QA Engineer: Duties & Responsibilities

Effectiveness of Quality Techniques

Cost of Fixing Defects• Fixing a defect in later phases costs more• One step techniques are cheaper than 2-

steps Inspection: symptoms and cause Testing: symptoms (more work to get root

cause) MS: 3 hrs to find and fix a bug by inspection MS: 12 to find and fix a bug with testing

SW QA Program must….

• Employ a variety of techniques to achieve higher-than-average quality Formal design inspections of the critical parts

of a system. Modeling or prototyping using a rapid

prototyping technique Code reading or inspections Execution testing