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Sept. 8, 2008 Seminar: Paderborn University Towards A Service-Oriented Approach to Testing Web Services Hong Zhu Department of Computing Oxford Brookes.

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Presentation on theme: "Sept. 8, 2008 Seminar: Paderborn University Towards A Service-Oriented Approach to Testing Web Services Hong Zhu Department of Computing Oxford Brookes."— Presentation transcript:

1 Sept. 8, 2008 Seminar: Paderborn University Towards A Service-Oriented Approach to Testing Web Services Hong Zhu Department of Computing Oxford Brookes University Oxford OX33 1HX, UK

2 Sept. 8, 2008 Seminar: Paderborn University Acknowledgement Mr. Qingning Huo, PhD student at Oxford Brookes University, UK Mr. Yufeng Zhang, MSc student at the National University of Defence Technology, China Dr. Sue Greenwood, Oxford Brookes University, UK

3 Sept. 8, 2008 Seminar: Paderborn University Overview Analyse the impact of the novel features of service-orientation on software testing Identify the requirements on infrastructural support to testing WS applications. Propose an framework to support testing WS Report some preliminary work

4 Sept. 8, 2008 Seminar: Paderborn University Characteristics of Web Services Web services is a distributed computing technique that offers more flexibility and looser coupling so that it is more suitable for internet computing. The dominant of program-to-program interactions The components of WS applications (such as service providers): 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.

5 Sept. 8, 2008 Seminar: Paderborn University 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 ProviderRequester Search for services registered services register service request service deliver service

6 Sept. 8, 2008 Seminar: Paderborn University A typical scenario Car Insurance Broker Suppose that a fictitious car insurance broker CIB is developing a web- based system that provides a complete service of car insurance. End users: Submit car insurance requirements to CIB Get quotes from various insurers Select one insurer to insure the car Submit payment information Get insurance document//confirmation Broker: Take information about the user and the car Check the validity of users information Get quotes from insurers and pass them to the user Get users selection of the insurer Get insurance from the insurer and pass the payment to the selected insurer Take commissions from the insurer or the user

7 Sept. 8, 2008 Seminar: Paderborn University Structure of the CIB application CIBs Services Bank Bs Services Insurance A 1 s Services Insurance A 2 s Services Insurance A n s Services GUI Interface CIBs 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

8 Sept. 8, 2008 Seminar: Paderborn University Testing own side services (1) Similar to test software components. Many existing work on software component testing can be applied or adapted with special considerations: The stateless feature of HTTP protocol; XML encoding of the data passing between services as in SOAP standard; Confirmation to the published descriptions: WSDL for the syntax of the services workflow specification in BPEL4WS semantic specification in e.g. OWL-S. These are the easy aspects to deal with, but…

9 Sept. 8, 2008 Seminar: Paderborn University Testing own side services (2) Dealing with requesters abnormal behaviours The requesters are autonomous, thus they may stop cooperation in the middle of a transaction for many reasons, such as intentional quit, network failure, or failures of requesters software system due to fault. Burdens are on the testers to ensure that the system handles such abnormal behaviours properly. Dealing with unexpected usages/loads As all web-based applications, load balance is essential. But, the knowledge of the usage of a WS may not be available during the design and implementation of the system. Dealing with incomplete systems A service may have to rely on other services to perform its functionality properly, 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 WS is dynamically bound to the other services, the knowledge of their format and semantics can only be based on assumptions and standards.

10 Sept. 8, 2008 Seminar: Paderborn University Testing of other side services in composition Some similarity to component integration, however, the differences are dominant Problems in the application of existing integration testing techniques: Lack of software artifacts Lack of control over test executions Lack of means of observation on system behaviour

11 Sept. 8, 2008 Seminar: Paderborn University 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 applicable Automatic instrumentation of original source code or executable code is not applicable For dynamic bound services, Human involvement in the integration becomes completely impossible. Possible solutions: (a) Derive test harness from WS descriptions; (b) The service provider to make the test stubs and drivers available for integration.

12 Sept. 8, 2008 Seminar: Paderborn University 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: Control over the execution has been essential to apply existing testing techniques and will continue to be essential for testing services: An invocation of the service as a test must be distinguished from 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 control the testing executions of the service. Currently, there is no support to such mechanisms in W3C standards of WS.

13 Sept. 8, 2008 Seminar: Paderborn University 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 Possible solutions: The service provider provides a mechanism and the services to the outside tester to observe its softwares 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.

14 Sept. 8, 2008 Seminar: Paderborn University 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, or by a third party. Independent testing services: Provider: 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.

15 Sept. 8, 2008 Seminar: Paderborn University Architecture of service oriented testing Broker T-services of A 1 F-services of A 1 Matchmaker UDDI Registry GUI F-services of Tester T 1 T-services of Tester T 1 F-services of Tester T 2 T-services of Tester T 2 T-services of A 2 F-services of A 2 Ontology management

16 Sept. 8, 2008 Seminar: Paderborn University Illustration of service oriented testing CIBs F-Services Bank Bs F-Services Insurance A 1 s F- Services Insurance A 2 s F- Services Insurance A n s F- Services GUI Interface WS Registry CIBs service requester Bank Bs T-Services Insurance A 1 s T- Services Insurance A 2 s T- Services Insurance A n s T- Services CIBs T-Services Tester T 1 F-Services Tester T 1 T-Services Test Broker F-Services Test Broker T-Services Tester T 2 F-Services Tester T 2 T-Services

17 Sept. 8, 2008 Seminar: Paderborn University 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

18 Sept. 8, 2008 Seminar: Paderborn University

19 Sept. 8, 2008 Seminar: Paderborn University Automating Test Services The key technique issues to enable automated online test of WS: How a testing service should be described, published and registered at WS registry; How a testing service can be 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).

20 Sept. 8, 2008 Seminar: Paderborn University 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

21 Sept. 8, 2008 Seminar: Paderborn University STOWS (1): Basic concepts Tester: a particular party who carries out a testing activity. Activity: consists of actions performed in testing process, including 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.

22 Sept. 8, 2008 Seminar: Paderborn University 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

23 Sept. 8, 2008 Seminar: Paderborn University STOWS (2): Compound concepts Capability: describes what a tester can do Capability MethodActivity EnvironmentContext Capability Data Artefact > Capability Data Type Input Output * 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

24 Sept. 8, 2008 Seminar: Paderborn University 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 Task MethodActivity EnvironmentContext Task Data Artefact > Task Data Type Input Output *

25 Sept. 8, 2008 Seminar: Paderborn University 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

26 Sept. 8, 2008 Seminar: Paderborn University Compound relations MorePowerful relation: between two capabilities. MorePowerful(c 1, c 2 ) means that a tester has capability c 1 implies that the tester can do all the tasks that can be done by a tester who has capability c 2. Contains relation: between two tasks. Contains(t 1, t 2 ) means that accomplishing task t 1 implies accomplishing t 2. 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 C2C2 C1C1 Task Contains T1T1 T2T2 C T Matches Match Contain * * * *

27 Sept. 8, 2008 Seminar: Paderborn University Definition of the MorePowerful relation A capability C 1 is more powerful than C 2, written MorePowerful(C 1, C 2 ), if and only if C 2 s capability is included in C 1 s activities C 1 and C 2 have the same context. Environment of C 1 is the enhancement of the environment of C 2. The method of C 2 is subsumed by C 1. For each input artefact of C 1, there is a corresponding compatible input in the input artefact of C 2 For each output artefact of C 2 there is a corresponding compatible output artefact of C 1.

28 Sept. 8, 2008 Seminar: Paderborn University Definition of the Contains relation A task T 1 contains task T 2, written Contains(T 1, T 2 ), if and only if T 1 and T 2 have the same context, T 1 s activities include and T 2 s activities, The method of T 1 subsumes the method of T 2, The environment of T 2 is an enhancement of the environment of T 1, For each input artefact of T 1, there is a corresponding compatible the input artefact of T 2, For each output artefact of T 2, there is a corresponding compatible the output artefact of T 1.

29 Sept. 8, 2008 Seminar: Paderborn University 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, Cs activities include Ts 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.

30 Sept. 8, 2008 Seminar: Paderborn University Properties of the compound relations (1) The relations MorePowerful and Contains are reflexive and transitive. (2) c 1, c 2 Capability, t Task, MorePowerful(c 1, c 2 ) Matches(c 2, t) Matches(c 1, t). (3) c Capability, t 1, t 2 Task, Contains(t 1, t 2 ) Matches(c, t 1 ) Matches(c, t 2 ).

31 Sept. 8, 2008 Seminar: Paderborn University 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.

32 Sept. 8, 2008 Seminar: Paderborn University Representation of STOWS in OWL-S Activity Context Environment Method Capability data Input Artefacts Output Artefacts ServiceCategory INPUT PARAMETERS ContextMark EnvironmentMark MethodMark Artefacts… OUTPUT PARAMETERS Artefacts… Capability Service profile

33 Sept. 8, 2008 Seminar: Paderborn University Case Study: Overview 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

34 Sept. 8, 2008 Seminar: Paderborn University Case study (1): The subject The subject CASCAT: Automated component testing tool for EJB Generate test cases from algebraic specification written in CASOCC Execution of EJB on test cases and reports errors if any axiom in the specification is violated Bo Yu, Liang Kong, Yufeng Zhang, and Hong Zhu, Testing Java Components Based on Algebraic Specifications, Proc. of ICST 2008, April 9-11, 2008, Lillehammer, Norway. Liang Kong, Hong Zhu and Bin Zhou, Automated Testing EJB Components Based on Algebraic Specifications, Proc. of TEST07/ COMPSAC07, Vol. 2, pp IEEE CS Press 2007.

35 Sept. 8, 2008 Seminar: Paderborn University Case study (2): Registry Service Profile of CASCAT ServiceCategory: TestCaseGenerationServices. Input artefact: specified by the class CasoccSpecification, which is a subclass of Specification and stands for algebraic specification in CASOCC. Context: ComponentTest. Environment: not limited. Method is CASOCC-method, which is a subclass of SpecificationBased method. Output artefact: test case.

36 Sept. 8, 2008 Seminar: Paderborn University Case study (3): Submitting search requests Test requester: a service was built that plays the role of test requester. It constructs test tasks and submits them to the test broker to search for a test service Test task that it produced is to generate test case from CASOCC specification in the context of the test as component test.

37 Sept. 8, 2008 Seminar: Paderborn University Example of test task fictitioustestcase.txt

38 Sept. 8, 2008 Seminar: Paderborn University Case study (4): Search and discovery Test Broker: Once receives a test task, it generates a capability description from the test task Constructs a Service Profile. Then calls the API of the Matchmaker Client to search for test service providers.

39 Sept. 8, 2008 Seminar: Paderborn University Case study (5): Invocation A Java Enterprise Bean was deployed on Jboss platform A formal specification of the bean was written in CASOCC. The web service of CASCAT is invoked as a web service to generate test case of the component. The result: Test cases as an instance of the OWL class TestCase. Stored as a file on a web server The Location attribute of the file is returned by the service.

40 Sept. 8, 2008 Seminar: Paderborn University Conclusion Testing imposes challenges to testing web services applications are analysed: Testing a web service as own software Solvable by adaption of existing software technologies Integration testing at development and at run-time No support in current WS standard stack Grant challenge to existing software testing technology A service oriented approach to solve the problem is proposed; Architecture fits well into service oriented architecture Supported by software testing ontology Feasibility of the approach tested via a case study.

41 Sept. 8, 2008 Seminar: Paderborn University 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

42 Sept. 8, 2008 Seminar: Paderborn University 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

43 Sept. 8, 2008 Seminar: Paderborn University 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 , 2008, Taiwan. In press. Zhu, H., A Framework for Service-Oriented Testing of Web Services, Proc. of COMPSAC06, Sept. 2006, pp 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, pp Zhu, H. Cooperative Agent Approach to Quality Assurance and Testing Web Software, Proc. of QATWBA04/COMPSAC04, Sept. 2004, IEEE CS, Hong Kong,pp Zhu, H., Huo, Q. and Greenwood, S., A Multi-Agent Software Environment for Testing Web-based Applications, Proc. of COMPSAC03, 2003, pp


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