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Struts 2 supports running unit tests of methods in the Struts Action class with the Struts 2 JUnit plugin. The JUnit plugin allows you to test methods of an Action class from within the Struts 2 framework. The Struts Servlet filter and interceptors fire just as if your application was running on a Servlet container.
The Struts 2 JUnit plugin jar file must be on your application's class path. In the example application (see info above) the pom.xml includes a dependency for the struts2-junit-plugin. There are numerous transitive dependencies, including to JUnit and the Spring framework.
In the example application, the Register Action class includes using the validate method. This method is automatically executed by the Struts 2 framework prior to the execute method. Additionally, this method needs the values from the user's input on the form to already have been provided to the instance fields of the Action class (this work is done by another Struts 2 interceptor). So it would be difficult to test the validate method without the overall Struts 2 framework running.
To use the Struts 2 plugin to ensure the Strut 2 framework runs as part of the test, you need to have your JUnit test class extend StrutsTestCase (see RegisterTest class in the example application).
To test the validate method we want Struts to call the Struts action that will cause the Action class's validate and execute methods to be run. In the example application this action is register.
Remember the validate method will be called automatically by the framework before calling the execute method. If validation fails the Struts framework will return "input". If there are no validation errors then the framework will call the execute method and return whatever String the execute method returns.
For our first test we'll test that there should be no validation errors. In the normal flow of this application the user would first enter the form data shown on the register.jsp page.
The input fields for the form have the following name values: personBean.firstName, personBean.lastName, personBean.email, and personBean.age. When the user fills out those fields Struts will take the values and provide them to the appropriate set methods of the personBean object. So as part of the test I need to simulate the user filling out these form fields. The StrutsTestCase provides a request object (of type MockHttpServletRequest) that I can use to set these values in the request scope.
The first statements in the test method use the request object to set the values of any request parameters. These simulate the values the user would enter into the form fields. Note how the first argument to setParameter is the same as the value of the name attribute in the Struts textfield tag in the register.jsp page.
In this test I'm providing good data for each form field as I want to ensure my validation doesn't register an error if the user provides correct information.
I then call the getActionProxy method with the argument of "/register.action" and then the getAction method to get a reference to the Struts action class for this test. This will ensure that the Struts 2 JUnit plugin will know which Action class should be used--the class associated with the register action in the struts.xml. In this case that class is the Register class.
The assertNotNull test ensures that argument to getActionProxy reference an Action class identified in struts.xml. It's a way of checking that you've correctly setup struts.xml for this action.
After that I can call actionProxy.execute(). This causes the Struts 2 framework to go through its normal process of Servlet fileter and interceptors for the action identified by the actionProxy (in this case that is the register.action). The validate method of class Register will get called and if it doesn't create any field or action errors then Struts 2 will call the execute method. In this example, the execute method should return "success".
So in the next statement, I check that success was returned.
To test that validation should fail, I just need to have a test method that doesn't provide input for a form field. For example, in the validate method of the Register Action class, is a test to ensure the user has entered some information for the personBean.firstName input field. In the test method I would just not use the request object to set a parameter for that field.
In the last assertEquals statement my test checks that the Struts 2 framework returned "input" as that is what the Struts 2 framework will return if the validation adds a field or action error.
There is much more you can do with the Struts 2 JUnit plugin to help you test the methods of your Action class in conjunction with the Struts 2 fraemwork. If your Struts 2 application uses Spring to inject dependencies into the Action class then the Struts 2 JUnit Plugin has a StrutsSpringTestCase that your test class should extend. Please read Testing Actions to learn more.