javax.servlet.JspException
is an exception that is defined in the JSP API. The JSP API is an extension of the Servlet API.
The reason why you don't experience this issue in JBoss 5.1 is because JBoss 5.1 contains jsp-api.jar
inside the JBOSS_HOME\common\lib
directory.
Just include the same jar as a dependency in your Struts test project.
I hope this helps.