module RSpec::Rails::ControllerExampleGroup::ClassMethods

def routes(&blk)

end
# ...

routes { MyEngine::Engine.routes }
describe MyEngine::PostsController do

@example

is most useful when testing Rails engines.
Specifies the routeset that will be used for the example group. This
def routes(&blk)
  before do
    self.routes = blk.call
  end
end