Webrat Webrat

in an rspec-rails view spec
where

  form.should have_selector("input",
    :type=>"text",
    :name => "site[site_name]",
    :value => "the site name"
    )

works correctly, testable by changing "text" to "textaaaaa" or similar causing a failure

using

  form.should have_tag("input",
    :type=>"text",
    :name => "site[site_name]",
    :value => "the site name"
    )

ignores the hash and does not cause a failure

I can't find any documentation for have_tag so I looked at the api code and it appeared to chain forward to have_selector so I expected the same behaviour.