After contacting Rick with my patch, he offered to give me commit access to the project. I took him up on the offer, so the layout assertion is now in there.
test_spec_on_rails is now on Git so unless you’re running Edge Rails you can’t use script/install to grab it. My suggestion is to clone from Git into vendor/plugins and then svn:ignore the .git file:
git clone git://github.com/pelargir/test_spec_on_rails.git vendor/plugins/test_spec_on_rails svn propset svn:ignore .git vendor/plugins/test_spec_on_rails