Okey, here's how I solved it:
In spec_helper.rb I defined the following method:
def content_for(name)
response.template.instance_variable_get("@content_for_#{name}")
end
Then in my examples I can just use this:
content_for(:sidebar).should have_tag('ul.people li.person', 2)
If anyone has a cleaner solution, please let me know.
/ CJ