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Lecture 8Lecture 8::Testing, Verification and ValidationTesting, Verification and Validation

Dr Valentina PlekhanovaDr Valentina Plekhanova

University of Sunderland, UKUniversity of Sunderland, UK

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Software Testing Fundamentals: Software Testing Fundamentals:

Some Testing TerminologySome Testing Terminology FaultsFaults - a mistake in the code that causes

the software to not behave as expected (causes).

FailuresFailures - the act of a product not behaving as expected - the manifestation of a fault (symptoms).

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Some Testing Terminology Some Testing Terminology ValidationValidation - establishing the fitness of a

software product for its use - "are we building the right product?"

VerificationVerification - establishing the correspondence between the software and its specification - "are we building the product right?"

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Some Testing Terminology Some Testing Terminology Test caseTest case - the collection of inputs,

predicted results and execution conditions for a single test.

Pass/fail criteriaPass/fail criteria - decision rules used to determine whether a product passes or fails a given test.

Test suiteTest suite - a collection of test cases necessary to "adequately" test a product.

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Some Testing TerminologySome Testing Terminology Test planTest plan - a document describing the

scope, approach, resources and schedule of intended testing activity - identifies features to be tested, the testing tasks, who will do each task, and any risks requiring contingency planning.

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Some Testing TerminologySome Testing Terminology Bug reportBug report - a method of transmitting

the occurrence of a discrepancy between actual and expected output to someone who cares for "follow-up" - also known as discrepancy report, defect report, problem report, etc.

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What is Software Testing?What is Software Testing? Process of executing a computer program and

comparing the actual behaviour with the expected behaviour.

The comparison is intended to detect deviations (if any) between the actual behaviour and the expected behaviour.

Testing serves as a barrier to allowing low quality products from reaching the customer.

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Testing Objectives Testing Objectives Testing is a process of executing a program

with the intent of finding an error. A benefit of testing is that it demonstrates

that the software appears to be working as stated in the specifications.

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Testing ObjectivesTesting Objectives The data collected through testing can also

provide an indication of the software's reliability and quality.

But, testing cannot show the absence of defect -- it can only show that software defects are present.

Functional Requirements and Non-functional Requirements must be tested.

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Software Testing is Not DebuggingSoftware Testing is Not Debugging TestingTesting establishes the existence of defects DebuggingDebugging is concerned with locating and

correcting these defects.

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software testing discovers unexpected behaviour; defect classification identifies the situation as a

software error, a design error, a specification error, a testing error, etc. - if available, a "work-around" is identified;

if a software error, then debugging is performed which tracks down the cause of the error, and attempts to fix it.

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The Testing ProcessThe Testing Process

Unit Testing

Sub-System Testing

System Testing

Acceptance Testing or Alpha Testing

Beta Testing

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The Testing Process: Major StagesThe Testing Process: Major Stages Unit TestingUnit Testing: Individual components are

tested to ensure that they operate correctly.  Module TestingModule Testing: A module is a collection

of dependent components such as an objects, procedures, and functions. A module encapsulates related components so can be tested without other system modules.

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The Testing ProcessThe Testing Process Sub-System TestingSub-System Testing: This phase involves

testing collections of modules, which have been integrated into sub-system. The sub-system test process should concentrate on the detection of interface errors by rigorously exercising these interfaces.

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The Testing Process: The Testing Process: System Testing

System TestingSystem Testing: The testing process is concerned with finding errors, which normally result from unanticipated interactions between sub-systems and components. It is also concerned with validating that the system meets its functional and non-functional requirements.

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The Testing Process:The Testing Process: Acceptance TestingAcceptance Testing

Acceptance TestingAcceptance Testing: Acceptance testing often reveals errors and omissions in the system requirements definition [Sommerville].

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The Testing ProcessThe Testing Process Acceptance testing is sometimes

called alpha testingalpha testing. When a system is to be marked as a

software product, a testing process called beta testingbeta testing is often used.

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The Testing Process: The Testing Process: Beta TestingBeta Testing Beta testingBeta testing involves delivering a

system to a number of potential customers who agree to use that system and to report problems to the system developers.

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The Testing Process: The Testing Process: Regression TestingRegression Testing Errors in program components may be

identified at the later stage of the testing process. Repairing program defects may introduce new defects so testing should be repeated after the system is modified. This is sometimes called regression testingregression testing [Sommerville].

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White Box Testing White Box Testing [Sommerville]

White box testing is an approach to testing where the tests are derived from knowledge of the software structure.

Test cases can be derived that guarantee that all independent paths within a module have

been exercised at least once; exercise all logical decisions on their true and false sides; execute all loops at their boundaries and within their

operational bounds; exercise internal data structures to ensure their validity.

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Black Box TestingBlack Box Testing Black box testingBlack box testing attempts to derive sets

of inputs that will fully exercise all the functional requirements of a system.

It is not an alternative to white box testing.

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Black Box TestingBlack Box Testing incorrect or missing functions; interface errors; errors in data structures or external

database access; performance errors; initialisation and termination errors.

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White Box & Black Box TestingWhite Box & Black Box Testing White box testing should be

performed early in the testing process, while black box testing tends to be applied during later stages.

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Tests are designed to answer the Tests are designed to answer the following questions:following questions: How is the function's validity tested? What classes of input will make good test cases? Is the system particularly sensitive to certain

input values? How are the boundaries of a data class isolated? What data rates and data volume can the system

tolerate? What effect will specific combinations of data

have on system operation?