15 oct. 2008 workshop on web service and testing 1 towards service-oriented testing of web services...

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Workshop on Web Service and Testing

1

Towards Service-Oriented Testing of Web Services

Hong ZhuDepartment of Computing, Oxford Brookes University

Oxford OX33 1HX, UK

Yufeng Zhang Dept of Computer Sci, National Univ. of Defense Tech., Cha

ngsha, China, Email: [email protected]

mailto:[email protected]

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2Workshop on Web Service and Testing

Overview

Motivation The impact of WS on software testing The requirements on supports to testing WS

Proposed frameworkPrototype implementation Case studies Conclusion

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Characteristics of Web ServicesThe components (services) of WS applications

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 services: 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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Testing developer’s own services

Service has similarity to test software components Many existing work on software component testing can be ap

plied or adapted

Requires special considerations: The stateless feature of HTTP protocol; XML encoding of the data passing between services as in SO

AP standard; Confirmation to the published descriptions:

WSDL for the syntax of the services workflow specification in BPEL4WS semantic specification in e.g. OWL-S.

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Testing developer’s own services (continue) Dealing with requesters’ abnormal behaviours

The requesters are autonomous, their behaviours may be unexpected

Need to ensure that the service handles abnormal behaviours properly

Dealing with unexpected usages/loads As all web-based applications, load balance is essential. The usage of a WS may not be available during the design an

d implementation of the system. Dealing with incomplete systems

A service may have to rely on other services, thus hard to separate the testing of the own services from the integration testing, especially when it involves complicated workflows.

In the worst case, when dynamically bound to the other services

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Testing of others’ services in composition

Some similarity to component integrationHowever, the differences are dominant Problems in the application of existing integratio

n testing techniques: Lack of software artifacts Lack of control over test executions Lack of means of observation on system behaviour

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Lack of software artifacts The problem:

No design documents, No source code, No executable code The impacts:

For statically bound services, Techniques that automatically derive stubs from source code are not a

pplicable Automatic instrumentation of original source code or executable code

is not applicable For dynamic bound services,

Human involvement in the integration becomes impossible. Possible solutions:

(a) Derive test harness from WS descriptions; (b) The service provider to make the test stubs and drivers available for integ

ration.

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Lack of control over test executions Problem:

Services are typically located on a computer on the Internet that testers have no control over its execution.

Impact: An invocation of the service as a test must be distinguished fr

om a real request of the service. System may be need to be restarted or put into a certain state

to test it. The situation could become much more complicated when a

WS is simultaneously tested by many service requesters. Possible solution:

The service provider must provide a mechanism and a service that enable service requesters to control the testing executions of the service.

Currently, there is no support to such mechanisms in W3C standards of WS.

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Lack of means of observation The problem:

A tester cannot observe the internal behaviours of the services The Impacts:

No way to measure test coverage No way to ensure internal state is correct

Possible solutions: The service provider provides a mechanism and the services t

o the outside tester to observe its software’s internal behaviour in order to achieve the test adequacy that a service requester requires.

The service provider opens its document, source code as well as other software artifacts that are necessary for testing to some trusted test service providers.

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The proposed approachA WS should be accompanied by a testing

service. functional services: the services of the

original functionalitytesting services: the services to enable test the

functional services

Testing services can be either provided by the same vendor of the functional services, or by a third party.

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Architecture of service oriented testing

Broker

T-services of A1

F-services of A 1

Matchmaker

UDDI Registry

GUI

F-services of Tester T1

T-services of Tester T1

F-services of Tester T2

T-services of Tester T2

T-services of A2

F-services of A 2

Ontology m

anagement

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A Typical Scenario: Car Insurance Broker

CIB’s F-Services

Bank B’s F-Services

Insurance A1’s F-Services

Insurance A2’s F-Services

Insurance An’s F-Services

GUI Interface

WS Registry

CIB’s service requester

Bank B’s T-Services

Insurance A1’s T-Services

Insurance A2’s T-Services

Insurance An’s T-Services

CIB’s T-Services

Tester T1 F-Services

Tester T1 T-Services

Test Broker F-Services

Test Broker T-Services

Tester T2 F-Services

Tester T2 T-Services

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How does it work?

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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Car Insurance Broker CIB

Insurer Web Service IS

(F- Service)

Test Broker: TB

.3.Request test service

Insurer Web Service: IS

(T- Service)

Matchmaker

Testing Service: TG ( Test case

Generator)

Testing Service: TE ( Test Executor)

8. Testing related meta-data

16. Test report

7. Request service meta-data

.

12. Testing related meta-data

0. Intended composition of services

9.Test case

6. Request test service

2 Registerservice

10. Request test service

15.Test results

1 Register service

5. List of testers

13. Test invocation of services

14. Results of test invocation of services

4. Search for testers

Test Broker

11. Request service meta-data

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Key Issues to Automate Test Services How a testing service should be described, published

and registered at WS registry; How a testing service can be searched and retrieved

automatically even for testing dynamically bound services;

How a testing service can be invoked by both a human tester and a program to dynamically discover a service and then test it before bind to it.

How testing results can be summarized and reported 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 (Zhu & Huo 2003, 2005).

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STOWS: Software Testing Ontology for WS Ontology defines the basic terms and relations

comprising the vocabulary of a topic area as well as the rules for combining them to define extensions to the vocabulary

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 divided into two

groups. Knowledge about software testing are also

represented as relations between concepts

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STOWS (1): Basic concepts Tester: a particular party who carries out a testing activity. Activity: consists of actions performed in testing process, inclu

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

Artefact: the files, data, program code and documents etc. inovlved in testing activities. An Artefact possesses an attribute Location expressed by a URL or a URI.

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 testing activities may occur in software development stages to achieve various testing purposes. Testing contexts typically include unit testing, integration testing, system testing, regression testing, etc.

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

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STOWS (2): Compound concepts

Capability: describes what a tester can do Capability

MethodActivity

Environment Context

Capability Data

Artefact

<<enumeration>>Capability Data Type

InputOutput

1 1

0-1 0-1

0-*

1-*

• 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

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Task: describes what testing service is requested

A testing activity to be performedHow the activity is to be

performed:the context the testing method to be usedthe environment in which the

activity must be carried outthe available resources the expected outcomes

Task

MethodActivity

Environment Context

Task Data

Artefact

<<enumeration>>Task Data Type

InputOutput

0-1 0-1

1 1 1-*

1-*

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STOWS (3): 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.

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Prototype Implementation

STOWS is represented in OWL-S Basic concepts as XML data definition Compound concepts defined as service profile

UDDI /OWL-S registry server (as the test broker): 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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Case Study: An automated software testing tool CASCAT is

wrapped into a test service Registered:

Capability is described in the ontology represented in OWL-S Searchable:

It can be searched when the testing task matches its capability Invoked through the internet

As a web services to generation test cases based on algebraic specification

A web service and its corresponding test service are implemented Both registered Testing of the WS can be invoked through the corresponding

T-Service

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ConclusionChallenges to testing web services applications

Testing a web service as developers’ own software Integration testing at development and at run-time

No support in current WS standard stack

A service oriented approach is proposed Architecture fits well into service oriented

architecture Supported by software testing ontology

Feasibility of the approach tested via a case study.

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Advantages Automated process to meet the requirements of on-the-

fly service integration testing Automation without human involvement Testing without interference to providing normal functional

services Testing without affect the real world state

Security and IPR can be managed through a certification and authentication mechanism for third party specialised testing services

Business opportunities for testing tool vendors and software testing companies to provide testing services online as web services

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Remaining challenges and future work Technical challenges

To develop a complete ontology of software testing (e.g. the formats of many different representations of testing related artefacts)

To implement the test brokers efficiently 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

Need standards, such as a standard of software testing ontology

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References Zhang, Y. and Zhu, H., Ontology for Service Oriented Testing of

Web Services, Proc. of The Fourth IEEE International Symposium on Service-Oriented System Engineering (SOSE 2008) , Dec. 18-19, 2008, Taiwan. In press.

Zhu, H., A Framework for Service-Oriented Testing of Web Services, Proc. of COMPSAC’06, Sept. 2006, pp679-691.

Zhu, H. and Huo, Q., Developing A Software Testing Ontology in UML for A Software Growth Environment of Web-Based Applications, Chapter IX: Software Evolution with UML and XML, Hongji Yang (ed.). IDEA Group Inc. 2005, pp263-295.

Zhu, H. Cooperative Agent Approach to Quality Assurance and Testing Web Software, Proc. of QATWBA’04/COMPSAC’04, Sept. 2004, IEEE CS, Hong Kong,pp110-113.

Zhu, H., Huo, Q. and Greenwood, S., A Multi-Agent Software Environment for Testing Web-based Applications, Proc. of COMPSAC’03, 2003, pp210-215.

15 oct. 2008 workshop on web service and testing 1 towards service-oriented testing of web services...

Documents

services service

service request service

service slide

service requesters

service description

service invocation

service registration

service providers