Spring: Using Mock Objects For Unit Testing MVC Controllers

Spring has a nice framework to unit test controller for web/rest applications and it integrates nicely with Junit.Assuming that you wrote a CustomerController for handling REST requests to create a customer. A basic CustomerController looks like this:

@Controller

@RequestMapping("/customers")

public class CustomerController {

@RequestMapping (method = RequestMethod.POST)

public void createCustomer(HttpServletRequest request,

                  HttpServletResponse response) {

//your code here

}

}

Now to test this controller using Spring Mock objects, the basic steps are as follows in your unit test:

Step1: Declare that you want to run test using JUnit. For example to run test using JUnit4 you need to use @RunWith annotation as follows:

@RunWith(SpringJUnit4ClassRunner.class)

public class CustomerControllerTest extends TestCase {

@Test

public void testCreateCustomer() throws Exception {

}

}

Step2: Specify the spring bean configuration using @ContextConfiguration so that Controller works from unit test.

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration("classpath:spring/customer/rest-config.xml")

public class CustomerControllerTest extends TestCase {

@Test

public void testCreateCustomer() throws Exception {

}

}

Step3: Setup DispatcherServlet. DispatchServlet will be used to send mock request to the controller. Setting up DispatchServlet requires implementing ApplicationContextAware.

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration("classpath:spring/customer/rest-config.xml")

public class CustomerControllerTest extends TestCase implements ApplicationContextAware {

private Servlet servlet;

 private ApplicationContext applicationContext;

@SuppressWarnings("serial")

@Before

private void init() {

servlet = new DispatcherServlet() {

@Override

protected WebApplicationContext createWebApplicationContext(

WebApplicationContext parent) throws BeansException {

GenericWebApplicationContext genericContext = new GenericWebApplicationContext();

genericContext.setParent(applicationContext);

genericContext.refresh();

return genericContext;

}

};

}

@Test

public void testCreateCustomer() throws Exception {

}

public void setApplicationContext(ApplicationContext arg0)

throws BeansException {

this.applicationContext = arg0;

}

}

Step4: Finally use MockHttpServletRequest to build the request, send it and process the response.

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration("classpath:spring/customer/rest-config.xml")

public class CustomerControllerTest extends TestCase implements ApplicationContextAware {

private Servlet servlet;

private ApplicationContext applicationContext;

@SuppressWarnings("serial")

@Before

private void init() {

servlet = new DispatcherServlet() {

@Override

protected WebApplicationContext createWebApplicationContext(

WebApplicationContext parent) throws BeansException {

GenericWebApplicationContext genericContext = new GenericWebApplicationContext();

genericContext.setParent(applicationContext);

genericContext.refresh();

return genericContext;

}

};

}

@Test

public void testCreateCustomer() throws Exception {

MockHttpServletRequest request = new MockHttpServletRequest();

// set uri, request parameter, request body, omitted here

MockHttpServletResponse response = new MockHttpServletResponse();

// send the request

MockServletConfig servletConfig = new MockServletConfig();

servlet.init(servletConfig);

servlet.service(request, response);

// validate response

String responseContent = response.getContentAsString();

int responseCode = response.getStatus();

}

public void setApplicationContext(ApplicationContext arg0)

throws BeansException {

this.applicationContext = arg0;

}

}

Promote your blog