Development of Software Testing Ontology and Application to Test Automation Prof. Hong Zhu Department of Computing and Electronics Oxford Brookes University

Development of Software Testing Ontology and

Application to Test Automation

Prof. Hong ZhuDepartment of Computing and Electronics

Oxford Brookes UniversityOxford OX33 1HX, UK

Email: [email protected]

Acknowledgement Mr. Yufeng Zhang, MSc and PhD student at the

National University of Defence Technology, China Mr. Qingning Huo, PhD student at Oxford Brookes

University, UK Dr. Sue Greenwood, Oxford Brookes University, UK

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2ONTOSE 2011, London

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Context: Web Services Web services is a distributed computing technique that

offers more flexibility and looser coupling based on the internet and web infrastructure.

The dominant of program-to-program interactions The components: (service providers, requesters, registry):

Autonomous: control their own resources and their own behaviours Active: execution not triggered by message, and Persistent: computational entities that last long time

Interactions between components: Social ability: discover and establish interaction at runtime Collaboration: as opposite to control, may refuse service, follow a

complicated protocol, etc.

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WS Technique Stack Basic standards:

WSDL: service description and publication UDDI: for service registration and retrieval SOAP for service invocation and delivery

More advanced standards for collaborations between service providers and requesters. BPEL4WS: business process and workflow models. OWL-S: ontology for the description of semantics of services

Registry

Provider Requester

Search for services

registered services

register service

request service

deliver service

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A Typical Scenario: Car Insurance Broker

CIB’s Services

Bank B’s Services

Insurance A1’s Services

Insurance A2’s Services

Insurance An’s Services

GUI Interface

CIB’s service requester

WS Registry

End users Other service users

Could be statically integrated

Should be dynamically integrated for business flexibility and competence, and lower operation and maintenance cost

Challenges to Testing WS Testing own side services

Mostly similar to test software components Some special issues, much work reported

Testing other side’s services Some similarity to component testing. The differences are

Lack of software artifacts Lack of control over test executions Lack of means of observation on system behaviour

Testing service composition Static composition: Mostly similar to integration test Dynamic composition: Most challenging, because

The need to deal with diversity The need of testing on-the-fly The need of non-intrusive testing The need of full automation

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The Proposed Approach A WS should be accompanied by a testing service

functional services: the services of the original functionality testing services: the services to enable test the functional services

Testing services can be either provided By the same vendor of the functional services By a third party

Independent testing services: Providers:

testing tool vendors companies of specialized in software testing

The services: to generate test cases to measure test adequacy to extract various types of diagrams from source code or design and

specification documents, etc.

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Architecture

Test BrokerTester T1

T-service of A1

F-service A1

Tester T2

T-service of A3

F-service A3

T-service of A2

F-service A2

Ontology M

anagement

UDDI Registry

Match maker

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Illustration in the Typical Scenario

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How Does the System Work?

The Scenario Suppose the car insurance broker want to search for

web services of insurers and test the web service before making quote for its customers.

Car Insurance Broker CIB

Insurer Web Service IS

customer

Information about the car and

the user

Insurance quotes

Testing the integration of two services

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Collaboration Process in the Typical Scenario

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Automating Test Services The key technique issues:

How to describe, publish and register test services at WS registry;

How to retrieve test services automatically for testing dynamically composed services;

How invoke test services by both a human tester and a program;

How to report test results in the forms that are suitable for both human beings to read and machine to understand

These issues can be resolved by the utilization of a software testing ontology.

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STOWS: Software Testing Ontology for WS

STOWS is base on an ontology of software testing originally developed for agent oriented software testing (Zhu & Huo 2003, 2005).• The concepts of software testing are

represented as classes • Knowledge about software testing are

represented as relations between concepts

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Basic Concepts of Software Testing Tester: who carries out a testing activity. Activity: actions performed in testing process, e.g.

test planning, test case generation, test execution, result validation, adequacy measurement and test report generation, etc.

Artifact: the entities used and/or produced by a testing activity, Location: expressed by a URL or a URI. Format: the format in which data are presented e.g. the files, data, program code and documents etc.

Method: the method used to perform a test activity. Test methods can be classified in a number of different ways.

Context: the context in which a testing activity is performed, e.g. in software development stages to achieve various testing purposes

Environment: The testing environment is the hardware and software configurations in which a testing is to be performed.

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Structure of Basic Concepts: Examples

Test Activity

Test planning

Test Case Generation

Test Execution

Result validation

Adequacy measurement

Report generation

Tester

Atomic Service

Composite Service

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Compound ConceptsCapability: describes what a tester can do

• the activities that a tester can perform • the context to perform the activity• the testing method used• the environment to perform the testing • the required resources (i.e. the input) • the output that the tester can generate

Capability

Activity Method

Artefact

Capability Data

Context Environment

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Task: describes what testing service is requested

A testing activity to be performed How the activity is to be performed:

the context the testing method to be used the environment in which the activity must be

carried out the available resources the expected outcomes

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Relations Between Concepts Relationships between concepts are a very important

part of the knowledge of software testing: Subsumption relation between testing methods Compatibility between artefacts’ formats Enhancement relation between environments Inclusion relation between test activities Temporal ordering between test activities

How such knowledge is used: Instances of basic relations are stored in a knowledge-base as

basic facts Used by the testing broker to search for test services through

compound relations

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Compound Relations MorePowerful relation: between two capabilities.

MorePowerful(c1, c2) means that a tester has capability c1 implies that the tester can do all the tasks that can be done by a tester who has capability c2.

Contains relation: between two tasks. Contains(t1, t2) means that accomplishing task t1 implies accomplishing t2.

Matches relation: between a capability and a task. Match(c, t) means that a tester with capability c can fulfil the task t.

Capability

Tester

MorePowerful

*

*IsMorePowerful

C2 C1

Task

ContainsT1

T2C TMatches

Match

Contain

* * **

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Definition of the MorePowerful Relation

A capability C1 is more powerful than C2, written MorePowerful(C1, C2), if and only if C2’s capability is included in C1’s activities C1 and C2 have the same context. Environment of C1 is the enhancement of the

environment of C2. The method of C2 is subsumed by C1. For each input artefact of C1 , there is a corresponding

compatible input in the input artefact of C2 For each output artefact of C2 there is a corresponding

compatible output artefact of C1.

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Definition of the Contains Relation

A task T1 contains task T2, written Contains(T1, T2), if and only if T1 and T2 have the same context, T1’s activities include and T2’s activities, The method of T1 subsumes the method of T2, The environment of T2 is an enhancement of the

environment of T1, For each input artefact of T1, there is a corresponding

compatible the input artefact of T2, For each output artefact of T2 , there is a corresponding

compatible the output artefact of T1.

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Definition of the Matches Relation

A capability C matches a task T, written Matches(C, T), if and only if

C and T have the same context, C’s activities include T’s activity, The method of C subsumes the method of T, The environment of T is an enhancement of

environment of C, For each input artefact of T , there is a corresponding

compatible input artefact of C, For each output artefact of C, there is a

corresponding compatible the output artefact of T.

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Properties of the Compound Relations

(1) The relations MorePowerful and Contains are reflexive and transitive.

(2) c1, c2Capability, tTask,

MorePowerful(c1, c2) Matches(c2, t)

Þ Matches(c1, t).

(3) cCapability, t1, t2Task,

Contains(t1, t2) Matches(c, t1)

Matches(c, t2).

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Prototype Implementation

Representation of STOWS in OWL Both basic and compound concepts are classes in

OWL and represented as XML data definitionUse STOWS in Semantic Web Services

Compound concepts represented in OWL are transformed into OWL-S Service Profile for registration, discovery and invocation UDDI /OWL-S registry server: using OWL-S/UDDI

Matchmaker• The environment: Windows XP, Intel Core Duo CPU

2.16GHz, Jdk 1.5, Tomcat 5.5 and Mysql 5.0.

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Transformation of STOWS in OWL-S

ActivityContextEnvironmentMethodCapability dataInput ArtefactsOutput Artefacts

ServiceCategoryINPUT PARAMETERS

ContextMark EnvironmentMark MethodMark Artefacts…OUTPUT PARAMETERS

Artefacts…

Capability Service profile

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Ontology Management Motivation

All the terms used in the capability description for test service registration, discovery and invocations must be first defined in the ontology.

However, it is impossible to build a complete ontology of software testing the huge volume of software testing knowledge the rapid development of new testing technique, methods and tools.

Therefore, the ontology must be extendable and open to the public for updating. To implement a framework, rather than a complete and fixed

ontology To provide an ontology management mechanism to enable

the population of the ontology

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The Ontology Management Mechanism It provides three services to users:

AddClass: to add new concept DeleteClass: to delete concept UpdateClass: to revise concept of the ontology

Restrictions on the manipulation of the data model Authority Checker:

elementary classes• form the framework of the ontology STOWS. • None of them could be pruned down

extended classes• attached to the elementary classes to define new concepts • instances of the concepts. • added by the users and can be deleted from the hierarchy

Conflict Checker the new class to be added does not exist in the ontology the class to be deleted has no subclasses in the hierarchy

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Structure of OMS

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Test Brokers

A test service that compose existing test services Decompose test tasks into subtasks Search for test services to carry out the subtasks Select test services from candidates Coordinate the selected test services

Invoke them in the right order Pass data between them Collects test results, etc.

Itself is a test service as well There may be multiple test brokers owned by

different vendors

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Architecture of the Prototype Test BrokerWe have developed a prototype test broker to

demonstrate the feasibility of the approach.

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Test broker process model

Select a T-service

Submit To Search Engine

Transform into Service Profile (by Matchmaker Client API)

User Requests a Test Task

Task (in OWL)

Test PlanSubtask 1Subtask 2

…Subtask n

Generate Test Plan

Tester Capability (In OWL)

Convert Test Task into Required Tester Capability

Service Profile (In OWL-S)

Matchmaker Returns

Research Results

List of Candidate T-Services

If Not Empty

SelectedT-Services

Profile for T-service Invocation (In OWL-S)

Execute T-Service

Submit to the T-service

Generate An Alternative Test Plan

Test ResultsIf successful

Select An Alternative T-Service

Set Profile parameters according to Task

If Empty

Report Test Results to The User

Test Report

If Failed

T-service Invocation Message (In XML)

Failure Message

If has alternative T-service

If no alternative T-service

A Running Example CIQS: the WS of the PingAn Insurance Company in China

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Test BrokerCIB: Car Insurance Broker

TCG: Test Case Generator

TCE: Test Case Executor for CIQS

CIQS: Car Insurance Quote Service

Matchmaker Request testing CIQS

Search testers

Invoke tester

Register

Case Study: Dealing with Diversity Aim: To evaluate the capability of dealing with diversity Method: To wrap a wide range of SW tools into test services

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Name Description

CASCAT A CASOCC-based test case generation tool

Test Case Format Translator

Translate the test case generated by CASCAT into the format recognizable by Calculator Test Case Executor

Test Case Executor Executes test case for a numeric calculator web service

Klee Generate and execute test cases from C source code by symbolic execution

Magic Check conformance between component specifications and their implementations

XML Comparator Compare XML files

Java NCSS Measure two standard metrics for Java program

Findbugs Find bugs in Java program by static analysis

PMDA static analysis tool for finding potential bugs and other problems in Java source code

WSDL Based Test Case Generator*

A WSDL based test case generation tool

Web Service Test Case Executor*

Execute the test case generated by WSDL Based Test Case Generator

Experiment 1: Dealing with Subtle Differences

Aim: To test the system’s capability of accurately

choosing an appropriate tester from those of subtle differences

Method: Application of the data mutation testing technique:

Mutation operators: transformations of data (service profiles in this case) (4 types )

Seeds: a set of original service profiles (11 seeds) Mutants: service profiles generated from the seeds by

applying mutation operators (167 mutants)

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Experiment 2: Scalability

Aim: To evaluate the scalability of test brokers in terms of its

efficiency to deal with test problems of practical sizes. Problem sizes in terms of

The number of testers in the registry The size of the knowledge-base in the test broker The complexity of test task requested

Method: To run the system for a number of times To calculate the average lengths of execution time spent

various modules of the test broker

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Experiment ResultsThe Effect of the Number of Testers

the average search time increases with the number of testers in the registry almost linearly.

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y = 0.0055x2 + 5.9023x + 280.6R² = 0.9935

0200400600800

10001200140016001800

0 20 40 60 80 100 120 140 160 180 200

Tim

e(m

s)

Number of Testers

Tester Searching TimeTrend Line

The Effect of the Knowledge-Base Size As the size of knowledge-base (in terms of the number of test

plan templates) increases, the time spent by the task analyzer module also increases, but in an almost linear rate.

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y = 3E-6x2 + 0.0809x + 2.2562R² = 0.9265

0

10

20

30

40

50

0 100 200 300 400 500

Tim

e(m

s)

Number of Plan Templates

Task Analysis Time

Trend Line

The Effect of Task Complexity The total execution time is a quadratic polynomial function

of the number of different subtasks (with R2=0.9984).

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y = 16.059x2 + 920.55x + 230.63R² = 0.9984

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5

Tim

e(m

s)

Number of Types of Subtasks

Testplan GenerationSearching for TestersInvocation of SubtasksTotal TimeTrend Line

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Conclusion The challenges imposed on testing web services can be

met by employing ontology of software testing to collaborate test services. Feasibility

tested by case studies with the prototype implementation Practical usability:

Implementable without any change to the existing standards of Semantic WS

Motivation for wider adoption by industry Business opportunities for testing tool vendors and

software testing companies to provide testing services online as web services

Scalable test services are distributed and there is no extra-burden

on UDDI servers.

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Future Work To populate the ontology of software testing (e.g. the

formats of many different representations of testing related artefacts)

To device the mechanism of certification and authentication for testing services

Social challenges: For the above approach to be practically useful, it must be adopted by web service developers, testing tool vendors and software testing companies

To improve the test broker, even to generalise it to all service composition Limitation of OWL-S semantic web services

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Related works Tsai et al. (2004): a framework to extend the function of UDDI to enable

collaboration Check-in and check-out services to UDDI servers

A service is added to UDDI registry only if it passes a check-in test. A check-out testing is performed every time the service is searched for. It is

recommended to a client only if it passes the check-out test. To facilitate such tests, they require test scripts being included in the information

registered for the WS on UDDI. Group testing: further investigation of the problem how to select a service from a

large number of candidates by testing. A test case ranking technique to improve the efficiency of group testing.

Bertolino et al (2005): audition framework an admission testing when a WS is registered to UDDI run time monitoring services on both functional and non-functional behaviours

after a service is registered in a UDDI server, Service test governance (STG) (2009):

to incorporate testing into a wider context of quality assurance of WS imposing a set of policies, procedures, documented standards on WS development, etc.

Bertolino and Polini admitted (2009), “on a pure SOA based scenario the framework is not applicable”.

Both recognised the need of collaboration in testing WS, the technical details about how to collaborate multiple parties in WS testing was left open.

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Thank You

Documents

Development of Software Testing Ontology and Application to Test Automation Prof. Hong Zhu Department of Computing and Electronics Oxford Brookes University