JMock Examples

JMock Examples

The following is a simple example of a servlet we will write unit tests for:

The servlet:
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;
import java.util.Map;

public class MyServlet extends HttpServlet {
    private MyService myService;
    public void setMyService(MyService myService) {
        this.myService = myService;
    }

    public void process(HttpServletRequest request, HttpServletResponse response) {
        String action = request.getParameter("action");
        if ("update".equals(action)) {
            Map parameters = request.getParameterMap();
            try {
                myService.updateModel(parameters);
            } catch (MyException e) {
                request.setAttribute("error", e.getMessage());
            }
        }
        request.setAttribute("model", myService.getModel());
        getServletContext().getRequestDispatcher("myView.jsp").forward(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        process(request, response);
    }
}

The unit test:
    * if the action is update, does it call myService.updateModel (example is below)
    * if myService.updateModel throws an exception does the response contain the exceptions message (not implemented below)
import org.jmock.Mock;
import org.jmock.MockObjectTestCase;
public class MyServletTest extends MockObjectTestCase {
    private Mock mockMyService;
    private Mock mockRequest;
    private Mock mockResponse;
    private MyService myService;
    private HttpServletRequest request;
    private HttpServletResponse response;
    private MyServlet myServlet;
    
    protected void setUp() throws java.lang.Exception {
        mockMyService = mock(MyService.class);
        mockRequest = mock(HttpServletRequest.class);
        mockResponse = mock(HttpServletResponse.class);
        myService = (MyService) mockMyService.proxy();
        request = (HttpServletRequest) mockRequest.proxy();
        response = (HttpServletResponse) mockResponse.proxy();
        myServlet = new MyServlet();
    }

    public void testUpdate() {
        // SETUP ANY OBJECTS USED ONLY IN THIS TESTCASE
        Map parameters = new Hashtable();
        // SETUP THE EXPECTED CALLS TO THE MOCK OBJECTS
        // setup the mock request object to have the getParameter
        // method called once with argument being equal to the
        // string action and have it return the string update
        mockRequest.expects(once()).method("getParameter").
            with(eq("action")).will(returnValue("update"));
        // setup the mock request object to have the getParameterMap
        // method called once with no arguments and have it
        // return an empty map
        mockRequest.expects(once()).method("getParameterMap")
            .will(returnValue(parameters));
        // setup the mock myService object to have the updateModel
        // method called once with the parameters map as the
        // argument
        mockMyService.expects(once()).method("updateModel").with(same(parameters));
        // setup the mock myService object to have the getModel
        // method called once with no arguments and have it
        // return an empty map
        mockMyService.expects(once()).method("getModel")
            .will(returnValue(parameters));
        // setup the mock myService object to have the updateModel
        // method called once with the parameters map as the
        // argument
        mockRequest.expects(once()).method("setAttribute").with(eq("model"), same(parameters));
        // RUN THE TEST
        // add the myService mock object to the servlet so
        // that it can handle calls later
        myServlet.setMyService(myService);
        myServlet.process(request, response);
    }
}