©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 1 Software inspections l Involve people examining the source representation with the aim of discovering anomalies and defects l Do not require execution of a system so may be used before implementation l May be applied to any representation of the system (requirements, design, test data, etc.) l Very effective technique for discovering errors

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 2 Inspection success l Many different defects may be discovered in a single inspection. In testing, one defect,may mask another so several executions are required l The reuse domain and programming knowledge so reviewers are likely to have seen the types of error that commonly arise

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 3 Inspections and testing l Inspections and testing are complementary and not opposing verification techniques l Both should be used during the V & V process l Inspections can check conformance with a specification but not conformance with the customer’s real requirements l Inspections cannot check non-functional characteristics such as performance, usability, etc.

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 4 Program inspections l Formalised approach to document reviews l Intended explicitly for defect DETECTION (not correction) l Defects may be logical errors, anomalies in the code that might indicate an erroneous condition (e.g. an uninitialised variable) or non-compliance with standards

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 5 Inspection pre-conditions l A precise specification must be available l Team members must be familiar with the organisation standards l Syntactically correct code must be available l An error checklist should be prepared l Management must accept that inspection will increase costs early in the software process l Management must not use inspections for staff appraisal

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 6 The inspection process

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 7 Inspection procedure l System overview presented to inspection team l Code and associated documents are distributed to inspection team in advance l Inspection takes place and discovered errors are noted l Modifications are made to repair discovered errors l Re-inspection may or may not be required

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 8 Inspection teams l Made up of at least 4 members l Author of the code being inspected l Inspector who finds errors, omissions and inconsistencies l Reader who reads the code to the team l Moderator who chairs the meeting and notes discovered errors l Other roles are Scribe and Chief moderator

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 9 Inspection checklists l Checklist of common errors should be used to drive the inspection l Error checklist is programming language dependent l The 'weaker' the type checking, the larger the checklist l Examples: Initialisation, Constant naming, loop termination, array bounds, etc.

Inspection checks

©Ian Sommerville 2000Software Engineering, 6th edition. Chapter 19Slide 11 Inspection rate l 500 statements/hour during overview l 125 source statement/hour during individual preparation l statements/hour can be inspected l Inspection is therefore an expensive process l Inspecting 500 lines costs about 40 man/hours effort = $$$