2011/08/05 - Jakarta Cactus has been retired.

How it works

Click here for a UML sequence diagram.

Let's go through the different steps to understand how it works. Here is what happens for each testXXX() method in your test case class (derived from YYYTestCase):

1. The JUnit Test Runner calls a YYYTestCase.runTest() method. This method first looks for a begin(WebRequest) method and executes it if found. Note that this method is called before each test. The WebRequest parameter passed to the beginXXX() method is used to set the HTTP headers, the HTTP parameters, ... that will be sent in step 2 to the Redirector proxy. The runTest() method then looks for a beginXXX(WebRequest) method and executes it if found.
2. The YYYTestCase.runTest() method then opens an HTTP connection to the Redirector proxy. All the parameters set up in the beginXXX() method are sent in the HTTP request (HTTP headers, HTTP parameters, ...)
3. The Redirector proxy acts as a proxy on the server side for your test case class. It means that your test case class is instantiated twice: once on the client side (by the JUnit Test Runner) and once on the server side (by the Redirector proxy). The client side instance is used for executing the begin(), beginXXX(), endXXX() and end() methods (see steps 1 and 8) and the server side instance is used for executing the testXXX() methods (see step 4). The Redirector proxy does the following:
   • creates an instance of your test class using reflection. It then sets specific implicit objects (which are class variables of YYYTestCase). These implicit objects depend on the redirector proxy (see next section).
   • creates instances of Cactus wrappers for some server objects (HttpServletRequest, ServletConfig, ServletContext, ...). This is to be able to to override some methods in order to return simulated values. For example, the Cactus framework can simulate an URI (i.e. act as if this URI was called instead of the Redirector proxy URI). Thus, the getServerName(), getServerPort(), getRequestURI(), ... methods return values based on the simulated URI (if there is any defined by the user).
   • creates an HTTP Session if the user has expressed the wish (using the WebRequest.setAutomaticSession(boolean) code in the beginXXX() method. By default a session is always created) and the redirector fills by reflection the session implicit object.
4. The setUp(), testXXX() and tearDown() methods of your test class are executed (in that order). They are called by the Redirector proxy using reflection. Of course, setUp() and tearDown() are optional (same as in JUnit).
5. Your testXXX() method calls your server side code to test, executing the test and using the JUnit assert API to assert the result (assert(), assertEquals(), fail(), ...)
6. If the test fails, your testXXX() methods throws exceptions which are caught by the Redirector proxy.
7. If an exception has been raised, the Redirector proxy returns the information about the exception (its name, class, stack trace) back to the client side. Information about the exception will then be printed by JUnit in its Test Runner console.
8. If no exception occurred, the YYYTestCase.runTest() method looks for an endXXX(org.apache.cactus.WebResponse) or endXXX(com.meterware.httpunit.WebResponse) method (this signature is used for HttpUnit integration) and executes it if found. At this stage, you have the opportunity to check returned HTTP headers, Cookies and the servlet output stream in the endXXX() method, again using JUnit asserts and helper utility classes provided by Cactus. Then the runTest() methods looks for an end(org.apache.cactus.WebResponse) or end(com.meterware.httpunit.WebResponse) method and calls it if found. This end() method is called after each test.

Redirector Proxies

Cactus provides 3 implementations of Redirector Proxies (see the TestCase Howto tutorial for more details on how to use these redirectors):

• A Servlet Redirector. This redirector is a servlet that should be used for unit testing servlet methods or any java class that uses servlet objects (HttpServletRequest, ...)
• A JSP Redirector. This redirector is a JSP page that should be used for unit testing server code that need access to JSP implicit objects (PageContext, ...). The JSP Redirector should be used to unit test custom Tag libraries.
• A Filter Redirector. This redirector is a Servlet Filter that should be uses for unit testing Servlet Filters or any java class that uses filter objects (FilterConfig, ...).

Servlet Redirector Proxy

The client side opens 2 HTTP connections to the Servlet redirector. Once to execute the tests and retrieve the servlet output stream and a second time to get the test result. This is to be able to get the exception data (message, stack trace, ...) if the test failed. The test results are stored in a variable which is put in the ServletContext and then retrieved on the second HTTP connection.

JSP Redirector Proxy

The client side opens 2 HTTP connections to the JSP redirector. Once to execute the tests and retrieve the servlet output stream and a second time to get the test result. This is to be able to get the exception data (message, stack trace, ...) if the test failed. The test results are stored in a variable which is put in the ServletContext and then retrieved on the second HTTP connection.

Filter Redirector Proxy

The client side opens 2 HTTP connections to the Filter redirector. Once to execute the tests and retrieve the servlet output stream and a second time to get the test result. This is to be able to get the exception data (message, stack trace, ...) if the test failed. The test results are stored in a variable which is put in the ServletContext and then retrieved on the second HTTP connection.