Unit testing a Java Servlet

Question

I would like to know what would be the best way to do unit testing of a servlet.

Testing internal methods is not a problem as long as they don't refer to the servlet context, but what about testing the doGet/doPost methods as well as the internal method that refer to the context or make use of session parameters?

Is there a way to do this simply using classical tools such as JUnit, or preferrably TestNG? Did I need to embed a tomcat server or something like that?

Answer 1

Most of the time I test Servlets and JSP's via 'Integration Tests' rather than pure Unit Tests. There are a large number of add-ons for JUnit/TestNG available including:

• HttpUnit (the oldest and best known, very low level which can be good or bad depending on your needs)
• HtmlUnit (higher level than HttpUnit, which is better for many projects)
• JWebUnit (sits on top of other testing tools and tries to simplify them - the one I prefer)
• WatiJ and Selenium (use your browser to do the testing, which is more heavyweight but realistic)

This is a JWebUnit test for a simple Order Processing Servlet which processes input from the form 'orderEntry.html'. It expects a customer id, a customer name and one or more order items:

public class OrdersPageTest {     private static final String WEBSITE_URL = "http://localhost:8080/demo1";      @Before     public void start() {         webTester = new WebTester();         webTester.setTestingEngineKey(TestingEngineRegistry.TESTING_ENGINE_HTMLUNIT);         webTester.getTestContext().setBaseUrl(WEBSITE_URL);     }     @Test     public void sanity() throws Exception {         webTester.beginAt("/orderEntry.html");         webTester.assertTitleEquals("Order Entry Form");     }     @Test     public void idIsRequired() throws Exception {         webTester.beginAt("/orderEntry.html");         webTester.submit();         webTester.assertTextPresent("ID Missing!");     }     @Test     public void nameIsRequired() throws Exception {         webTester.beginAt("/orderEntry.html");         webTester.setTextField("id","AB12");         webTester.submit();         webTester.assertTextPresent("Name Missing!");     }     @Test     public void validOrderSucceeds() throws Exception {         webTester.beginAt("/orderEntry.html");         webTester.setTextField("id","AB12");         webTester.setTextField("name","Joe Bloggs");          //fill in order line one         webTester.setTextField("lineOneItemNumber", "AA");         webTester.setTextField("lineOneQuantity", "12");         webTester.setTextField("lineOneUnitPrice", "3.4");          //fill in order line two         webTester.setTextField("lineTwoItemNumber", "BB");         webTester.setTextField("lineTwoQuantity", "14");         webTester.setTextField("lineTwoUnitPrice", "5.6");          webTester.submit();         webTester.assertTextPresent("Total: 119.20");     }     private WebTester webTester; }