CS352 – Software Engineering II Lecture 17: SW Quality Assurance Landscape Slides by Mohammad El-Ramly, PhD

حديث شريف 1.إن الله يحب إذا عمل أحدكم عملا أن يتقنه 2.إن الله كتب الإحسان على كل شئ

Lecture 17 Outline 1.Understanding SW Quality Attributes 2.Understand the value of SW QA 3.Quality Landscape 4.SW QA Jobs and Certificates 5.Effectiveness of QA Techniques Readings are essential for this course. Reading: (7) Code Complete Chapter 20 Accompanying site:

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 & Planning 2.Explicit QA Activities 3.Testing Strategy 4.SE Guidelines 5.Formal / Informal Technical Reviews 6.Change-control Procedures 7.Measurement of Results 8.Prototyping

Software Quality Landscape Planning Requirements Design Development Testing Guidelines, Standards and Templates QA Planning and Budgeting Testing Debugging Reviews Refactoring Requirements V & V Design Review Collaborative Development / Reviews Metrics Change and Configuration Management Bug Tracking Surveys Deployment & Maintenance M a n a g e m e n t Contract Review

1. SW Quality Objectives Decide explicit quality characteristics 1.Inform the developers 2.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

CS 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 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 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