From the errors you're getting, my guess is that somewhere within the WebSphere
Test Environment, the Struts 1.1 jar is getting loaded prior to the Struts 1.2 jar.
Here's something you may want to try:
Use the import wizard to import the struts-blank.war file that comes with the Struts 1.2 download. Then copy all of your classes and other files from the old project to the new project and see if you get the same error.
Let me know if this fixes it