Chapter 8 Software Quality Assurance

1. Chapter 8Software Quality Assurance

2. Quality Concepts • general objective: reduce the “variation between samples” ... but how does this apply to software? • quality control: a series of inspections, reviews, tests • quality assurance: analysis, auditing and reporting activities • cost of quality • appraisal costs • failure costs • external failure costs

3. Why SQA Activities Pay Off? cost to find and fix a defect 100 60.00-100.00 log scale 10.00 10 3.00 1.50 1.00 0.75 1 test Design field system Req. use code test

4. Software Quality Assurance SQA Process Definition & Standards Formal Technical Reviews Analysis & Reporting Test Planning & Review Measurement

5. Role of SQA Group • Prepare SQA project plan • Assist with developing project sw process description • Review sw eng. activities to verify compliance w/defined sw process • Audit designated sw work products • Ensure that deviations in sw and work products are documented/handled IAW docum. Process • Record any non-compliance and report it to senior mgmt

6. Reviews & Inspections ... there is no particular reason why your friend and colleague cannot also be your sternest critic. Jerry Weinberg

7. What Are Reviews? • a meeting conducted by technical people for technical people • a technical assessment of a work product created during the software engineering process • a software quality assurance mechanism • a training ground

8. What Reviews Are Not! They are not: a project budget summary a scheduling assessment an overall progress report a mechanism for reprisal or political intrigue!!

9. The Players review leader standards bearer (SQA) producer maintenance oracle reviewer recorder user rep

10. Conducting the Review be prepared—evaluate 1. product before the review review the product, not 2. the producer keep your tone mild, ask 3. questions instead of making accusations stick to the review agenda 4. 5. raise issues, don't resolve them 6. avoid discussions of style—stick to technical correctness 7. schedule reviews as project tasks 8. record and report all review results

11. Review Options Matrix * IPR WT IN RRR trained leader agenda established reviewers prepare in advance producer presents product “reader” presents product recorder takes notes checklists used to find errors errors categorized as found issues list created team must sign-off on result IPR—informal peer review WT—Walkthrough IN—Inspection RRR—round robin review yes yes yes no yes yes yes yes yes yes yes yes yes no no yes no no yes maybe no maybe maybe maybe no maybe no no no no yes yes yes yes no yes no no yes yes *

12. Metrics Derived from Reviews inspection time per page of documentation inspection time per KLOC or FP inspection effort per KLOC or FP errors uncovered per reviewer hour errors uncovered per preparation hour errors uncovered per SE task (e.g., design) number of minor errors (e.g., typos) number of major errors (e.g., nonconformance to req.) number of errors found during preparation

13. • collect information on all defects • find the causes of the defects • move to provide fixes for the process Statistical SQA Product & Process measurement ... an understanding of how to improve quality ...

14. Misc. Topics • Reliability • “the probability of failure-free program in a specified environment for a specified time” [Musa] • Availability • SW Safety [Leveson] • ID hazards, categorize by criticality, risk • Analyze to assign severity and probability • Specify safety-related requirements

15. More Misc. Topics • Poka-yoke devices • ISO-9000 • Telecom equip., medical devices • Suppliers • Optional on own • ISO-9001 • SQA Plan