It looks like the behavior of the 'testrb' command has changed which
is causing Rake to no longer work with Test::Unit when trying to add
options such as "--runner=gtk2".

Apparently, you used to have to call testrb as follows:

    testrb /path/to/test/case -- --runner=gtk2

(at least, that's the impression I got from the Rake docs.)

This will produce a LoadError as Test::Unit tries to load the file '--
--runner=gtk2'.

Changing the call to this:

    testrb /path/to/test/case --runner=gtk2

seems to work just fine.

Here's the simple patch against testtask.rb to get it working again
(not _thoroughly_ tested, YMMV):

    89c89
    <       testoptions = " -- #{get_options}"
    ---
    >       testoptions = " #{get_options}"

-- 
Regards,
John Wilger

-----------
Alice came to a fork in the road. "Which road do I take?" she asked.
"Where do you want to go?" responded the Cheshire cat.
"I don't know," Alice answered.
"Then," said the cat, "it doesn't matter."
- Lewis Carrol, Alice in Wonderland