Verification and ValidationObjectivesTopics coveredVerification vs validationThe V & V processV& V goalsV & V confidenceStatic and dynamic verificationStatic and dynamic V&VProgram testingTypes of testingTesting and debuggingThe debugging processV & V planningThe V-model of developmentThe structure of a software test planThe software test planSoftware inspectionsInspection successInspections and testingProgram inspectionsInspection pre-conditionsThe inspection processInspection procedureInspection rolesInspection checklistsInspection checks 1Inspection checks 2Inspection rateAutomated static analysisStatic analysis checksStages of static analysisSlide 33LINT static analysisUse of static analysisVerification and formal methodsArguments for formal methodsArguments against formal methodsCleanroom software developmentThe Cleanroom processCleanroom process characteristicsFormal specification and inspectionsCleanroom process teamsCleanroom process evaluationKey pointsSlide 46©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 1Verification and Validation©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 2ObjectivesTo introduce software verification and validation and to discuss the distinction between themTo describe the program inspection process and its role in V & VTo explain static analysis as a verification techniqueTo describe the Cleanroom software development process©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 3Topics coveredVerification and validation planningSoftware inspectionsAutomated static analysisCleanroom software development©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 4Verification: "Are we building the product right”.The software should conform to its specification.Validation: "Are we building the right product”.The software should do what the user really requires.Verification vs validation©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 5Is a whole life-cycle process - V & V must be applied at each stage in the software process.Has two principal objectives•The discovery of defects in a system;•The assessment of whether or not the system is useful and useable in an operational situation.The V & V process©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 6V& V goalsVerification and validation should establish confidence that the software is fit for purpose.This does NOT mean completely free of defects.Rather, it must be good enough for its intended use and the type of use will determine the degree of confidence that is needed.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 7V & V confidenceDepends on system’s purpose, user expectations and marketing environment•Software function•The level of confidence depends on how critical the software is to an organisation.•User expectations•Users may have low expectations of certain kinds of software.•Marketing environment•Getting a product to market early may be more important than finding defects in the program.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 8Software inspections. Concerned with analysis of the static system representation to discover problems (static verification)•May be supplement by tool-based document and code analysisSoftware testing. Concerned with exercising and observing product behaviour (dynamic verification)•The system is executed with test data and its operational behaviour is observedStatic and dynamic verification©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 9Static and dynamic V&VFormalspecificationHigh-leveldesignRequirementsspecifi cationDetaileddesignProgramPrototypeProg ramtestingSoftwareinspections©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 10Can reveal the presence of errors NOT their absence.The only validation technique for non-functional requirements as the software has to be executed to see how it behaves.Should be used in conjunction with static verification to provide full V&V coverage.Program testing©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 11Defect testing•Tests designed to discover system defects.•A successful defect test is one which reveals the presence of defects in a system.•Covered in Chapter 23 Validation testing•Intended to show that the software meets its requirements.•A successful test is one that shows that a requirements has been properly implemented.Types of testing©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 12Defect testing and debugging are distinct processes.Verification and validation is concerned with establishing the existence of defects in a program.Debugging is concerned with locating and repairing these errors.Debugging involves formulating a hypothesis about program behaviour then testing these hypotheses to find the system error.Testing and debugging©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 13The debugging processLocateerrorDesignerror repairRepairerrorRetestprogramTestresultsSpecificationTestcases©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 14Careful planning is required to get the most out of testing and inspection processes.Planning should start early in the development process.The plan should identify the balance between static verification and testing.Test planning is about defining standards for the testing process rather than describing product tests.V & V planning©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 15The V-model of developmentSystemspecifi cationSystemdesignDetaileddesignModule andunit codeand testSub-systemintegrationtest planSystemintegrationtest planAcceptancetest planServiceAcceptancetestSystemintegration testSub-systemintegration testRequirementsspecifi cation©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 22 Slide 16The structure of a software test planThe testing process.Requirements traceability.Tested items.Testing schedule.Test recording procedures.Hardware and