{cactus}ServletTestRequest::addParameter help

[cmedcoff]

Can someone please answer a couple questions regarding the Cactus architecture? I am writing a test suite to test a data validation routine in my servlet. I am passing a number of parameters in a single request. For each test, I want to send one of the parameters with invalid data. I created a function that uses the ServletTestRequest's addParameter method to initially set up valid default parameters for each data item. For each test in the suite, I want to reset to invalid data the single item being tested. Unfortunately, there does not appear to be a  method for setting, changing, or removing a parameter from the request once it has been added. Is there a reason that this functionality is not provided? Also, according to the documentation, it is possible to add the same parameter name several times to the request. Under what circumstances would someone want to do this? Can you give me an example?  I appreciate any help you can give.