ServletTestCase Principles

Last update : September 25 2001

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  • When to use ?

    Your test case class should extend ServletTestCase whenever you are unit testing :

    • Servlets,
    • Any java code that uses Servlet API objects (HttpServletRequest, ...)

    Provided Implicit Objects

    Cactus automatically initializes the implicit objects for you and they are made available to your setUp(), testXXX() and tearDown() methods as instance variables of the ServletTestCase class (and thus as instance variables of your test case class as it extends ServletTestCase).

    Note You may ask yourself how Cactus initializes these objects. The mechanism is described in the How it works guide.

    The provided implicit objects are :


    Instance variable name   request  
    Class name   org.apache.cactus.server.HttpServletRequestWrapper , which inherits from javax.servlet.http.HttpServletRequest  

    Cactus wraps methods of the original HTTP request in order to return the HTTP related parameters set up in the beginXXX() method. Thus, you will be able to pass this request object to your code to test and set the needed parameter in the beginXXX() method.

    For example, if your code under test calls getCookies() on the request object that you have passed to it, it will return the cookies that you have added to the HTTP request in beginXXX() by calling the WebRequest.addCookie() method.

    See the javadoc for the org.apache.cactus.WebRequest and org.apache.cactus.server.HttpServletRequestWrapper classes for all details. You should also look at the samples provided in the Cactus distribution.


    Instance variable name   response  
    Class name   javax.servlet.http.HttpServletResponse  

    Note Cactus does not wrap the response.


    Instance variable name   config  
    Class name   org.apache.cactus.server.ServletConfigWrapper , which inherits from javax.servlet.ServletConfig  

    Cactus wraps the original Servlet Config for two reasons :

    • In order to provide additional methods. For example, it is possible to initialise parameters without setting them in web.xml, etc...,
    • So that it can return a wrapped Servlet Context instead of the original one. This is because the Servlet Context is used to perform forwards and includes and we need to pass to these methods the original request and response. As we have wrapped the request, we need to wrap the Servlet Context to pass the original request (and not the wrapped one).

    The config implicit object will contain all initialisation parameters defined in web.xml under the Servlet Redirector servlet definition.

    See the javadoc for the org.apache.cactus.server.ServletConfigWrapper class for all details. You should also look at the samples provided in the Cactus distribution.


    Instance variable name   session  
    Class name   javax.servlet.http.HttpSession  

    Note Cactus does not wrap the response.

    By default, Cactus always creates an HTRP session for your test case. It is possible to tell it not to do so by calling the WebRequest.setAutomaticSession(false) method (it is true by default). This could be useful for cases where your code under test verifies branches when "request.getSession(false)" is null.

    Tips and Tricks

    Parameter initialisation

    If your code under test make use of any of the servlet methods inherited from javax.servlet.GenericServlet (these are the log(), getServletConfig(), ... methods), then you need to call the init(ServletConfig) method of your servlet to initialise its internal ServletConfig object.

    For example :

    public void testXXX()
        MyServletToTest servlet = new MyServletToTest();
        // Call a method to test that uses a method inherited from Generic Servlet

    See the samples provided as part of the Cactus distribution.


    This is a very basic sample intended to give you a flavour of Servlet unit testing. Check the distribution samples for extensive examples.

    Note This example is for Cactus 1.2 as it uses the new WebRequest and WebResponse objects.

    public void beginXXX(WebRequest theRequest)
        // Set up HTTP related parameters
        theRequest.setURL("", "/mywebapp", "/test/test.jsp",
            null, null);
        theRequest.addCookie("cookiename", "cookievalue");
    public void testXXX()
        MyServletToTest servlet = new MyServletToTest();
        // Call method to test
        // Perform some server side asserts
        assertEquals("someValue", session.getAttribute("someAttribute"));
        assertEquals("", request.getServerName());
    public void endXXX(WebResponse theResponse)
        // Asserts the returned HTTP response
        Cookie cookie = theResponse.getCookie("someCookie");
        assertEquals("someValue2", cookie.getValue());
        assertEquals("some content here", theResponse.getText());

    Copyright © 2000-2001 The Apache Software Foundation. All Rights Reserved.