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Software Testing and Quality Assurance

Lecture 29 - Introduction to Software Testing

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Lecture Outline Introduction to testing types. Testing activities. Introduction to test cases, test oracles

and their execution.

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Testing Policy Only exhaustive testing can show a program is

free from defects. However, exhaustive testing is impossible;

Testing policies define the approach to be used in selecting system tests; For example, All functions accessed through menus should be

tested; Combinations of functions accessed through the

same menu should be tested; Where user input is required, all functions must be

tested with correct and incorrect input.

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Software Testing & Development Life Cycle

Requirements

ArchitecturalDesign

Detail Design

Implementation

Unit Testing

IntegrationTesting

System Testing

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Unit Testing

modulemoduleto beto betestedtested

test casestest cases

resultsresults

softwaresoftwareengineerengineer

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Unit Testing

interface interface local data structureslocal data structures

boundary conditionsboundary conditionsindependent pathsindependent pathserror handling pathserror handling paths

modulemoduleto beto betestedtested

test casestest cases

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Unit Testing

ModuleModule

stubstub stubstub

driverdriver

RESULTSRESULTS

interface interface

local data structureslocal data structures

boundary conditionsboundary conditions

independent pathsindependent paths

error handling pathserror handling paths

test casestest cases

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Integration Testing Involves building a system from its

components and testing it for problems that arise from component interactions.

Top-down integration Develop the skeleton of the system and populate it

with components. Bottom-up integration

Integrate infrastructure components then add functional components.

To simplify error localisation, systems should be incrementally integrated.

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Integration Testing The Big-bang Approach. Incremental Approach.

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Top-Down Integration

top module is tested with top module is tested with stubsstubs

stubs are replaced one at stubs are replaced one at a time, "depth first"a time, "depth first"

as new modules are integrated, as new modules are integrated, some subset of tests is re-runsome subset of tests is re-run

AA

BB

CC

DD EE

FF GG

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Bottom-Up Integration

drivers are replaced one at a drivers are replaced one at a time, "depth first"time, "depth first"

worker modules are grouped into worker modules are grouped into builds and integratedbuilds and integrated

AA

BB

CC

DD EE

FF GG

clustercluster

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Thread-Based Integration

Top modules areTop modules aretested tested withwith stubs stubs

Worker modules are grouped into Worker modules are grouped into builds and integratedbuilds and integrated

AA

BB

CC

DD EE

FF GG

clustercluster

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System Testing System Functional Test

Test entire system against the functional requirements.

System Performance Test Test the non-functional requirements of the

system. For example, Response times, load testing etc.

System Acceptance Test Set of tests that the software must pass before it is

accepted by the client.

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Trivial Example You have been asked to write a term paper on ‘Integration

Testing in Component Based System’. To do this, you need to find references from a range of library databases.

You logs on to the KFUPM library system and uses the search facility to find relevant papers from IEEE, ACM and Elsevier databases.

One paper of special interest requires authentication and you have to fill an online form to receive the paper.

If you are allowed, the paper will be downloaded and ready for collection.

An email will be send to you once the paper is ready.

Scenario-based Testing

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Student Activity Identify the possible interactions for the

system testing of library system.

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Trivial Example - System Testing Test the login mechanism using correct and

incorrect login. Test the search facility using queries against

known source to check that the search mechanism is actually documents.

Test system presentation facility to check that information about documents is displayed properly.

Test the mechanism to request permission for downloading.

Test the e-mail response indicating that the download document is available.

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Regression Testing Change do not always effect the entire

program. Change in one part of system can effect

other part. After each change

Entire test suite of a system must be run again.

Need for an automatic test suite execution.

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Test Activities Boils down to selecting and executing

test cases. Test case consists of…… Set of test inputs, of if the program is non-

terminating, a sequence of test inputs. Expected results when the inputs are

executed; and Execution conditions or execution

environment in which the inputs are to be executed.

These steps generally remain same from unit testing to system testing.

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Test Case Selection Coverage criterion;

Equivalence Partitioning Boundary-Value Analysis Coverage-Based Testing

Control-flow Data-flow

Expected behavior of every test input to be generated. (Test Oracles)

Testing environment.

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Test Oracles Determines whether or not the program

has passed or failed the test case. A test oracle is

A program A process A body of data

In many cases - directly form the requirements. For example, a test case assessing

performance - performance threshold.

Difficult to automate or to assess their quality

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Test Execution Test inputs on the ‘program-under-test’

Record the actual behavior.

Generally can be automated to an extend !!!!

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Test Evaluation Compare the actual behavior with the

expected behavior.

Generally can be automated to an extend !!!!

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Test Reporting Report the outcome of the testing.

Developers Project Mangers etc.

Generally can be automated to an extend !!!!

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Key Points A system typically undergoes a range of

testing types. Each type of testing is aimed at

detecting different kinds of failures. Testing boils down to the selection and

execution of test cases.