running single functional test doesn't work

running :

ruby -Itest test/functional/partners_controller_test.rb -
should_create_partner
runs all functional tests in partners_controller_test.rb

ruby -Itest test/functional/partners_controller_test.rb -n
should_create_partner
doesn't run anything at all

but it's clearly stated in the doc :

You can also run a particular test method from the test case by using
the -n switch with the test method name.
ruby -Itest test/unit/post_test.rb -n test_the_truth

is tr true ONLY for test/unit ???

thanks for feedback