Dr. Dobb's Journal - November 2008 - (Page 48)

Best Practices Special TESTING SERVICE-ORIENTED ARCHITECTURES continued from page 46 boundaries of the system of interest be simulated. For proxies to deliver meaningful content to these services, realistic data must be obtained. This can be done by monitoring the node that is transmitting the data and copying before sending the data forward. The proxy could then leverage the sample data for testing purposes. One means of generating proxies is to use DII and Dynamic Service Interfaces (DSI) and the interface definition. Pulling previously collected data from a data store provides an approximation of the actual service. A mechanism should be able to toggle between live or simulated data. Similarly, it should be possible to use the proxies to simulate network load and latency. In addition to proxies, agents can be added to services through plug-in mechanisms. Agents allow monitoring of service inputs and outputs. Additionally, they can be used to monitor various metrics, such as time of processing or network behavior. The granularity of the agent (as a proxy, or else embedded in the service) would allow precise monitoring at multiple levels. If agents possess XPath and XQuery ability, then content validation can be executed too. Code-Level Change and Instrumentation When source code is available, test harness frameworks can perform code-level monitoring using utility classes or code instrumentation. One approach to code-level monitoring is to use aspects. In addition to introducing cross-cutting into the source code, aspect frameworks (such as AspectJ) can instrument libraries. Consequently, support for pointcuts and joinpoints can be introduced at a code level as needed. To reduce overhead, the aspect could be written to pass information to a separate monitoring program. Another useful outcome of such a tool is coverage testing of services in a dynamic service composition environment. This enables an understanding of compositions favored by processes and an insight into which services are used or avoided by user communities. test harness in Ruby (www2.ruby-lang .org/en/). We decided that Ruby’s dynamic programming and metaprogramming features would be useful in creating a harness that could add methods declaratively at runtime. Since our team consisted of Java developers trying Ruby for the first time, we decided to use JRuby (jruby.codehaus.org). This let us incorporate well-understood Java frameworks from within the Ruby source. Using SOAP4R (dev.ctor.org/soap4r), we wrote a SOAP Client. Data was then recorded from an existing Apache Axis2 service. The output was saved using YAML (www .yaml.org), a powerful human-readable data serialization mechanism available with Ruby implementations. We also used SOAP4R to create a standalone SOAP Server. Methods to be tested and the corresponding results were maintained as key-value pairs in a Java properties file. The format of each key-value pair is: methodname_param1param2 paramN=recorded_response.yml A Test Harness in Ruby To test some of these ideas, my team implemented a simple record-and-playback style #read the methods and responses from test.properties fis = FileInputStream.new("test.properties") @properties = Properties.new @properties.load(fis) fis.close keys = @properties.keys #add methods to return the recorded response keys.each do |key| puts "Adding method " + key.to_s add_method(self,key.to_s, Object.new) self.class.send('define_method', key.to_s) { |*args| if (@properties.containsKey(key.to_s)) value= @properties.get(key) puts "Found operation " + key.to_s + " with value " + value.to_s #retrieve the data from the saved result if (value) if (value.rindex('.yml') > 0) data = YAML::load_file(value) return data else file = File.new(value) data = file.readlines file.close return data end end end } end Example 1: Code fragment to add methods. driver = SOAP::RPC::Driver.new( 'http://localhost:8080/axis2/services/WeatherService', 'http://ws.apache.org/axis2') #driver = SOAP::RPC::Driver.new( 'http://localhost:9080/','urn:weatherSoapServer') driver.add_method('getWeather') file = File.new('getweather.yml','w') YAML.dump(driver.getWeather,file) file.close Example 2: Client code to store service output. If desired, we could have extended the format to refer to specific service URIs as well. Finally, we added methods at runtime using Ruby’s metaprogramming facilities. Example 1 created the methods. The Java classes (Properties, FileInputStream) are leveraged by way of JRuby. Example 2 presents the corresponding client code used to record data from the web service. While this example is simple, it provides the skeleton of a test harness for services. With moderate effort, you can extend it to encompass multiple services with multiple methods. Consequently, the server can be used to create a boundary of services to be invoked by the service(s) under study. To the best of my knowledge, there are two commercial off-the-shelf solutions that provide this sort of functionality exist— iTKO’s LISA (www.itko.com) and AmberPoint’s Validation (www.amberpoint.com/ products/validation.shtml). Both provide Service Virtualization to varying degrees. While Amberpoint’s solution is a development time record-and-playback utility, iTKO’s solution also has elements for continuous testing of services. DDJ 48 Dr. Dobb’s Journal l www.ddj.com l November 2008 http://www2.ruby-lang.org/en/ http://www2.ruby-lang.org/en/ http://jruby.codehaus.org http://dev.ctor.org/soap4r http://www.yaml.org http://www.yaml.org http://www.itko.com http://www.amberpoint.com/products/validation.shtml http://www.amberpoint.com/products/validation.shtml 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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