[Webtest] How to use setcheckbox correctly?

[webtest@lists.canoo.com]

Hi,

I've some trouble with setcheckbox using a property like this:

        <setcheckbox stepid="${test.name} - Set checkbox"
            name="unique" checked="${unique.value}" />

This works fine as long as unique.value=true, but when it's false I get
following error:

    Test step clickbutton named "MoveFromYoutilityCurrentNotUnique - Push
button continue to page3" 
    failed with message "Could not remove parameter from request: unique"


So I though that I have to preset the checkbox beforehand, leading to
following steps:

        <setcheckbox stepid="${test.name} - Set checkbox"
            name="unique" checked="true" />

        <setcheckbox stepid="${test.name} - Set checkbox"
            name="unique" checked="${unique.value}" />

Now, again this works fine, but only when unique.value=false, else I get
following error:

    Exception raised:
com.meterware.httpunit.FormParameter$UnusedParameterValueException: 
    Attempted to assign to parameter 'unique' the extraneous value 'on'.


Am'I missing something, or does it means that one cannot use setcheckbox in
a generic way?

thanks and regards
Robert