Chapter 8 Software Quality Assurance

Software Quality Assurance Software requirements Specified standards – development criteria Implicit requirements

Cost of Quality Prevention costs Appraisal costs Quality planning Formal technical reviews Test equipment Training  Appraisal costs In-process and interprocess inspection Equipment calibration and maintenance Testing 

Internal failure costs Failure mode analysis  Repair Rework External failure costs Complaint resolution Product return and replacement Help line support Warranty work

Responsibility Project managers Software engineers SQA team Salespeople Customers

Quality Management & Software Development

SQA Activities Prepares an SQA plan for a project to the software project team. Participates in the development of the project’s software process description. Reviews software engineering activities to verify compliance with the defined software process. Audits designated software work products to verify compliance with those defined as part of the software process. Ensures that deviations in software work and work products are documented and handled according to a documented procedure. Records any noncompliance and reports to senior management.

Software Review

Why To error is human Large classes of errors escape the originator mare easily than they escape anyone else. Defect amplification

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 1 0.75 Design test field Req. system code use test

Defect Amplification P.542 sommer

P.542 sommer

Formal Technical Reviews (FTR) Objectives of FTR: to uncover errors to verify requirements to ensure predefined standards to achieve uniform manner to make more manageable

The Players review leader producer reviewer recorder

Conducting the Review 1. be prepared—evaluate product before the review 2. review the product, not the producer 3. keep your tone mild 4. stick to the review schedule 5. raise issues, don't resolve them 6. record and report all review results

Review Summary Report What was reviewed? Who reviewed it? What were the findings and conclusions?

Review Guidelines Review the product, not the producer. Set an agenda and maintain it. Limit debate and rebuttal. Enunciate/specify problem areas, but don't attempt to solve every problem noted. Take written notes. Limit the number of participants and insist upon advance preparation. Develop a checklist for each product that is likely to be reviewed. Allocate resources and schedule time for FTRs. Conduct meaningful training for all reviewers. Review your early reviews.

Statistical SQA measurement • collect and categorize information on all defects Product & Process • find the causes of the defects • using Pareto principle • move to provide fixes measurement ... an understanding of how to improve quality ...

Example

Causes Incomplete or erroneous specification (IES) Misinterpretation of customer communication (MCC) Intentional deviation from specifications (IDS) Violation of programming standards (VPS) Error in data representation (EDR) Inconsistent component interface (ICI) Error in design logic (EDL) Incomplete or erroneous testing (IET) Inaccurate or incomplete documentation (IID) Error in programming language translation of design (PLT) Ambiguous or inconsistent human/computer interface (HCI) Miscellaneous (MIS)

Phase & Error Index Phase Index PIi = ws(Si/Ei) + wm(Mi/Ei) + wt(Ti/Ei) Error Index EI = (i x PIi) / PS Ei = total number of errors uncovered during the ith step Si = the number of serious errors Mi = the number of moderate errors Ti = the number of minor errors ws, wm, wt = weighting factors for serious, moderate, and trivial errors PS = size of the product

Software Reliability & Availability MTBF = MTTF + MTTR MTBF: Mean Time between failure MTTF: Mean Time To Failure MTTR: Mean Time To Repair  Availability Availability =[MTTF/(MTTF + MTTR)] x 100%

SQA plan The plan identifies Evaluations to be performed Audits and reviews to be performed Standards that are applicable to the project Procedures for error reporting and tracking Documents to be produced by the SQA group Amount of feedback provided to the software project team p.201

IEEE SQA Plan

The ISO 9000 Quality Standards 20 requirements: management responsibility quality system contract review design control documents and data control product identification …