This file tests for a duplicate tag attribute.

<input jwcid="@TextField" value="ognl:emailAddress" type="text" name="emailaddress" id="emailaddress"  size="10" maxlength="25" value='' />

One possible scenario, designer gives developer a page with a long <input> tag.
Developer adds jwcid and ognl expression for 'value' but misses the fact that
there is already a 'value' attribute. Unless this case was handled as an error, the TemplateParser
will silently throw away the first 'value' attribute and bind the parameter statically.
This hurts in, say, a TextField as Tapestry dumps an exception page when it tries to update
value's binding, which is static and does not allow this.
    
Tough to track down as, in this case, the stack trace shows that AbstractBinding.setString()
throwing the exception. This kills newbies!