Dr. Dobb's Journal - November 2008 - (Page 53)

by Paul Hamill Best Practices Special Unit Testing Web Services Bringing Agile practices to service-oriented application development Web services (WS) are becoming a key architectural aspect of large-scale distributed applications. Technology leaders are both launching service-centric applications, such as Google Earth, eBay Web Services, and Amazon’s E-Commerce Service, and creating tools that enable other organizations to publish web services. The standards-based, fault-tolerant, self-describing nature of web services enable the creation of loosely coupled applications that run on heterogeneous systems. Web services also enable interoperability between different online applications and enable innovative, synergistic combinations: mashups. While the prime directive for developers once was “put it on the Internet” the main goal now is often to “make it a Service , Oriented Architecture (SOA).” For Agile developers, following best practices by doing TestDriven Development (TDD) of WS code can require extra effort, but is definitely feasible. In this article, I present techniques and patterns for unit testing WS applications to enable TDD as well as general-purpose testing. Paul is a senior developer with more than 20 years of experience writing software. His book Unit Test Frameworks discusses unit testing and Agile development from a language-independent perspective. He can be contacted at paul.hamill.3@gmail.com. Web service applications are inherently multitier. The remote code calling the service methods can be a user’s browser-based client or desktop application. It could also be another web service; Tim Berners-Lee and others have stated their expectations that the future Semantic Web will be based on automated agents exchanging information via web services (see “The Semantic Web,” www.sciam.com/article.cfm?id= the-semantic-web). Service methods are implemented by the service interface, which contains functionality to generate, send, and receive messages. The service interface is distinct from the service’s application logic, and in some cases, is automatically generated based on a service description in Web Services Description Language (WSDL) or a similar schema. So, every WS application has at least three tiers: the service application, the service interface, and the client interface. In Figure 1, MyService is the service interface layer, MyApp is the service application, and ServiceStub is the client interface that enables remote code to call the web service. MyService implements the WS messaging, while MyApp contains application logic, business rules, data persistence, and other service implementation layers. continued on page 56 November 2008 l www.ddj.com l Dr. Dobb’s Journal 53 http://www.sciam.com/article.cfm?id=the-semantic-web http://www.sciam.com/article.cfm?id=the-semantic-web http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - November 2008

Dr. Dobb's Journal - November 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Developer's Notebook Saving Open Source Conversations iPhone Building Your Own Web Server Green Telnet What's New In Boost Threads? Testing Service Oriented Architectures Test Case Generation, UML, and Eclipse Unit Testing Web Services C3 Programming The Agile Edge Swaine's Flames Effective Concurrency

Dr. Dobb's Journal - November 2008

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