Dr. Dobb's Journal - November 2008 - (Page 56)

Best Practices Special UNIT TESTING WEB SERVICES continued from page 53 WS messages may contain complex objects serialized as XML, or simple HTTP GET/POST operations. Although it can be tempting to trust that WS messaging just works, generation and communication of such messages represents a significant potential point of failure, and screams for test coverage (at least for followers of the Agile testing mantra, “only the paranoid survive.”) Because web services are a presentation layer of sorts, representing the front end of the WS application from the client’s perspective, they can be tested using an approach that is analogous to testing GUI code (see Agile User Interface Development, www.onjava.com/pub/a/ onjava/2004/11/17/agileuser_1.html), by separating the presentation layer from the application logic. In this case, the presentation layer is the WS messaging functionality. Following this approach, each method and behavior of the web service interface should have corresponding tests. However, to validate how the service methods work “over the wire,” it’s not sufficient just to create an instance of the service interface class and invoke its methods directly. The service methods must be validated by calling them via the client interface, the same way they are called in the live application. In addition to verifying the end-to-end functionality of the service methods, this also permits test- ing additional behaviors of the service, such as service resources, client connections, timeouts, and error handling. For these reasons, it is important to test SOA Listing One public class MyServiceTest extends TestCase { public void setUp() { String URI = "http://localhost/services/MyService"; // create service endpoint and connect to URI MyService service = endpoint.getMyService(); } public void testGetDoc() { service.putDoc( "test" ); assertEquals( "test", service.getDoc() ); } public void tearDown() { service.destroy(); } } Listing Two Listing Three public class MyServiceTest extends TestCase { public void testGetImage() { GetImageResponse r = service.getImage( "test.image.1" ); assertEquals( 72000, r.getData().length ); } } Listing Four public class MyServiceTest extends TestCase { public void testInvalidLogin() { try { service.login( "not_a_real_login", "bad_password" ); fail( "Expected LoginException not thrown" ); } catch ( LoginException e ) {} // expected exception } } Figure 1: Top-level components of a typical web service application. Listing Five Figure 2: Test class MyServiceTest, which tests web service methods by calling an instance of the service running in a service container. public class MyServiceTest extends TestCase { public void testTimeout() { service.setTimeout( Calendar.SECOND, 1 ); try { Thread.sleep(1010); // wait for timeout } catch (InterruptedException e) {} try { service.putDoc( "test" ); // try to call service fail( "Expected RemoteException not thrown" ); } catch ( RemoteException e ) {} // expected exception } } Listing Six public class MyServiceTest extends TestCase { public void testMultipleConnections() { MyService service1 = endpoint.getMyService(); MyService service2 = endpoint.getMyService(); service1.putDoc( "test" ); assertFalse( "test" == service2.getDoc() ); } } Figure 3: Service interface MyService and its test class MyServiceTest. 56 Dr. Dobb’s Journal l www.ddj.com l November 2008 http://www.onjava.com/pub/a/onjava/2004/11/17/agileuser_1.html http://www.onjava.com/pub/a/onjava/2004/11/17/agileuser_1.html 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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