def test_create_with_empty_email_sets_error_in_flash
post :create
assert_not_nil flash[:error]
end

(from Carlos Brando’s free book: Ruby On Rails 2.1 - What’s new)

In the end I ended doing something like:

class SomeController < ApplicationController
def some_action
…
flash_now(:notice, “hello”)
end

private
def flash_now(key, something)
flash.now[key] = something
end
end

Then I could spec the action with something like

it “should blah blah”
…
controller.should_receive(:flash_now).with(:notice, “Hello”)
end

May not be the best example (you can argue now the problem is testing flash_now method ) but what I try to say is that sometimes is easier to change a little the code to make it more “testable”.